[v1,2/2] serial: 8250: Extract platform driver

Extract platform driver to a separate module for better maintenance
and to reduce churn on 8250_core part changes when it's solely related
to the former. No functional changes intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/tty/serial/8250/8250.h          |  22 +-
 drivers/tty/serial/8250/8250_core.c     | 342 +-----------------------
 drivers/tty/serial/8250/8250_platform.c | 339 +++++++++++++++++++++++
 drivers/tty/serial/8250/Makefile        |   5 +-
 4 files changed, 369 insertions(+), 339 deletions(-)
 create mode 100644 drivers/tty/serial/8250/8250_platform.c

Hi Andy,

Many thanks for helping with this!. Just few questions below for my
understanding.

On Mon, May 06, 2024 at 05:00:59PM +0300, Andy Shevchenko wrote:
> Extract platform driver to a separate module for better maintenance
> and to reduce churn on 8250_core part changes when it's solely related
> to the former. No functional changes intended.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/tty/serial/8250/8250.h          |  22 +-
>  drivers/tty/serial/8250/8250_core.c     | 342 +-----------------------
>  drivers/tty/serial/8250/8250_platform.c | 339 +++++++++++++++++++++++
>  drivers/tty/serial/8250/Makefile        |   5 +-
>  4 files changed, 369 insertions(+), 339 deletions(-)
>  create mode 100644 drivers/tty/serial/8250/8250_platform.c
> 
> diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h
> index ac218412e54e..e5310c65cf52 100644
> --- a/drivers/tty/serial/8250/8250.h
> +++ b/drivers/tty/serial/8250/8250.h
> @@ -9,7 +9,7 @@
>  
>  #include <linux/bits.h>
>  #include <linux/serial_8250.h>
> -#include <linux/serial_reg.h>
> +#include <linux/serial_core.h>
>  #include <linux/dmaengine.h>
>  
>  #include "../serial_mctrl_gpio.h"
> @@ -93,6 +93,10 @@ struct serial8250_config {
>  #define UART_BUG_THRE	BIT(3)	/* UART has buggy THRE reassertion */
>  #define UART_BUG_TXRACE	BIT(5)	/* UART Tx fails to set remote DR */
>  
> +/* Module parameters */
> +#define UART_NR	CONFIG_SERIAL_8250_NR_UARTS
> +
> +extern unsigned int nr_uarts;
>  
>  #ifdef CONFIG_SERIAL_8250_SHARE_IRQ
>  #define SERIAL8250_SHARE_IRQS 1
> @@ -100,6 +104,9 @@ struct serial8250_config {
>  #define SERIAL8250_SHARE_IRQS 0
>  #endif
>  
> +extern unsigned int share_irqs;
> +extern unsigned int skip_txen_test;
> +
>  #define SERIAL8250_PORT_FLAGS(_base, _irq, _flags)		\
>  	{							\
>  		.iobase		= _base,			\
> @@ -111,7 +118,19 @@ struct serial8250_config {
>  
>  #define SERIAL8250_PORT(_base, _irq) SERIAL8250_PORT_FLAGS(_base, _irq, 0)
>  
> +extern struct uart_driver serial8250_reg;
> +void serial8250_register_ports(struct uart_driver *drv, struct device *dev);
> +
> +/* Legacy ISA bus related APIs */
> +typedef void (*serial8250_isa_config_fn)(int, struct uart_port *, u32 *);
> +extern serial8250_isa_config_fn serial8250_isa_config;
> +
> +void serial8250_isa_init_ports(void);
> +
> +extern struct platform_device *serial8250_isa_devs;
> +
>  extern const struct uart_ops *univ8250_port_base_ops;
> +extern struct uart_ops univ8250_port_ops;
>  
>  static inline int serial_in(struct uart_8250_port *up, int offset)
>  {
> @@ -201,6 +220,7 @@ static inline bool serial8250_clear_THRI(struct uart_8250_port *up)
>  	return true;
>  }
>  
> +struct uart_8250_port *serial8250_setup_port(int index);
>  struct uart_8250_port *serial8250_get_port(int line);
>  
>  void serial8250_rpm_get(struct uart_8250_port *p);
> diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
> index 51432f89919c..192f8d19d2fe 100644
> --- a/drivers/tty/serial/8250/8250_core.c
> +++ b/drivers/tty/serial/8250/8250_core.c
> @@ -6,11 +6,9 @@
>   *
>   *  Copyright (C) 2001 Russell King.
>   *
> - *  Supports: ISA-compatible 8250/16550 ports
> - *	      PNP 8250/16550 ports
> + *  Supports:
>   *	      early_serial_setup() ports
>   *	      userspace-configurable "phantom" ports
> - *	      "serial8250" platform devices
>   *	      serial8250_register_8250_port() ports
>   */
>  
> @@ -36,47 +34,13 @@
>  #include <linux/string_helpers.h>
>  #include <linux/uaccess.h>
>  #include <linux/io.h>
> -#ifdef CONFIG_SPARC
> -#include <linux/sunserialcore.h>
> -#endif
>  
>  #include <asm/irq.h>
>  
> -#include "../serial_base.h"	/* For serial_base_add_isa_preferred_console() */
> -
>  #include "8250.h"
>  
> -/*
> - * Configuration:
> - *   share_irqs - whether we pass IRQF_SHARED to request_irq().  This option
> - *                is unsafe when used on edge-triggered interrupts.
> - */
> -static unsigned int share_irqs = SERIAL8250_SHARE_IRQS;
> -
> -static unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS;
> -
> -static struct uart_driver serial8250_reg;
> -
> -static unsigned int skip_txen_test; /* force skip of txen test at init time */
> -
>  #define PASS_LIMIT	512
>  
> -#include <asm/serial.h>
> -/*
> - * SERIAL_PORT_DFNS tells us about built-in ports that have no
> - * standard enumeration mechanism.   Platforms that can find all
> - * serial ports via mechanisms like ACPI or PCI need not supply it.
> - */
> -#ifndef SERIAL_PORT_DFNS
> -#define SERIAL_PORT_DFNS
> -#endif
> -
> -static const struct old_serial_port old_serial_port[] = {
> -	SERIAL_PORT_DFNS /* defined in asm/serial.h */
> -};
> -
> -#define UART_NR	CONFIG_SERIAL_8250_NR_UARTS
> -
>  struct irq_info {
>  	struct			hlist_node node;
>  	int			irq;
> @@ -342,7 +306,7 @@ static void univ8250_release_irq(struct uart_8250_port *up)
>  }
>  
>  const struct uart_ops *univ8250_port_base_ops = NULL;
> -static struct uart_ops univ8250_port_ops;
> +struct uart_ops univ8250_port_ops;
>  
>  static const struct uart_8250_ops univ8250_driver_ops = {
>  	.setup_irq	= univ8250_setup_irq,
> @@ -370,22 +334,12 @@ struct uart_8250_port *serial8250_get_port(int line)
>  }
>  EXPORT_SYMBOL_GPL(serial8250_get_port);
>  
> -static void (*serial8250_isa_config)(int port, struct uart_port *up,
> -	u32 *capabilities);
> -
> -void serial8250_set_isa_configurator(
> -	void (*v)(int port, struct uart_port *up, u32 *capabilities))
> -{
> -	serial8250_isa_config = v;
> -}
> -EXPORT_SYMBOL(serial8250_set_isa_configurator);
> -
>  static inline void serial8250_apply_quirks(struct uart_8250_port *up)
>  {
>  	up->port.quirks |= skip_txen_test ? UPQ_NO_TXEN_TEST : 0;
>  }
>  
> -static struct uart_8250_port *serial8250_setup_port(int index)
> +struct uart_8250_port *serial8250_setup_port(int index)
>  {
>  	struct uart_8250_port *up;
>  
> @@ -410,59 +364,7 @@ static struct uart_8250_port *serial8250_setup_port(int index)
>  	return up;
>  }
>  
> -static void __init serial8250_isa_init_ports(void)
> -{
> -	struct uart_8250_port *up;
> -	static int first = 1;
> -	int i, irqflag = 0;
> -
> -	if (!first)
> -		return;
> -	first = 0;
> -
> -	if (nr_uarts > UART_NR)
> -		nr_uarts = UART_NR;
> -
> -	/*
> -	 * Set up initial isa ports based on nr_uart module param, or else
> -	 * default to CONFIG_SERIAL_8250_RUNTIME_UARTS. Note that we do not
> -	 * need to increase nr_uarts when setting up the initial isa ports.
> -	 */
> -	for (i = 0; i < nr_uarts; i++)
> -		serial8250_setup_port(i);
> -
> -	/* chain base port ops to support Remote Supervisor Adapter */
> -	univ8250_port_ops = *univ8250_port_base_ops;
> -	univ8250_rsa_support(&univ8250_port_ops);
> -
> -	if (share_irqs)
> -		irqflag = IRQF_SHARED;
> -
> -	for (i = 0, up = serial8250_ports;
> -	     i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;
> -	     i++, up++) {
> -		struct uart_port *port = &up->port;
> -
> -		port->iobase   = old_serial_port[i].port;
> -		port->irq      = irq_canonicalize(old_serial_port[i].irq);
> -		port->irqflags = 0;
> -		port->uartclk  = old_serial_port[i].baud_base * 16;
> -		port->flags    = old_serial_port[i].flags;
> -		port->hub6     = 0;
> -		port->membase  = old_serial_port[i].iomem_base;
> -		port->iotype   = old_serial_port[i].io_type;
> -		port->regshift = old_serial_port[i].iomem_reg_shift;
> -
> -		port->irqflags |= irqflag;
> -		if (serial8250_isa_config != NULL)
> -			serial8250_isa_config(i, &up->port, &up->capabilities);
> -
> -		serial_base_add_isa_preferred_console(serial8250_reg.dev_name, i);
> -	}
> -}
> -
> -static void __init
> -serial8250_register_ports(struct uart_driver *drv, struct device *dev)
> +void __init serial8250_register_ports(struct uart_driver *drv, struct device *dev)
>  {
>  	int i;
>  
> @@ -619,7 +521,7 @@ console_initcall(univ8250_console_init);
>  #define SERIAL8250_CONSOLE	NULL
>  #endif
>  
> -static struct uart_driver serial8250_reg = {
> +struct uart_driver serial8250_reg = {
>  	.owner			= THIS_MODULE,
>  	.driver_name		= "serial",
>  	.dev_name		= "ttyS",
> @@ -720,120 +622,6 @@ void serial8250_resume_port(int line)
>  }
>  EXPORT_SYMBOL(serial8250_resume_port);
>  
> -/*
> - * Register a set of serial devices attached to a platform device.  The
> - * list is terminated with a zero flags entry, which means we expect
> - * all entries to have at least UPF_BOOT_AUTOCONF set.
> - */
> -static int serial8250_probe(struct platform_device *dev)
> -{
> -	struct plat_serial8250_port *p = dev_get_platdata(&dev->dev);
> -	struct uart_8250_port uart;
> -	int ret, i, irqflag = 0;
> -
> -	memset(&uart, 0, sizeof(uart));
> -
> -	if (share_irqs)
> -		irqflag = IRQF_SHARED;
> -
> -	for (i = 0; p && p->flags != 0; p++, i++) {
> -		uart.port.iobase	= p->iobase;
> -		uart.port.membase	= p->membase;
> -		uart.port.irq		= p->irq;
> -		uart.port.irqflags	= p->irqflags;
> -		uart.port.uartclk	= p->uartclk;
> -		uart.port.regshift	= p->regshift;
> -		uart.port.iotype	= p->iotype;
> -		uart.port.flags		= p->flags;
> -		uart.port.mapbase	= p->mapbase;
> -		uart.port.mapsize	= p->mapsize;
> -		uart.port.hub6		= p->hub6;
> -		uart.port.has_sysrq	= p->has_sysrq;
> -		uart.port.private_data	= p->private_data;
> -		uart.port.type		= p->type;
> -		uart.bugs		= p->bugs;
> -		uart.port.serial_in	= p->serial_in;
> -		uart.port.serial_out	= p->serial_out;
> -		uart.dl_read		= p->dl_read;
> -		uart.dl_write		= p->dl_write;
> -		uart.port.handle_irq	= p->handle_irq;
> -		uart.port.handle_break	= p->handle_break;
> -		uart.port.set_termios	= p->set_termios;
> -		uart.port.set_ldisc	= p->set_ldisc;
> -		uart.port.get_mctrl	= p->get_mctrl;
> -		uart.port.pm		= p->pm;
> -		uart.port.dev		= &dev->dev;
> -		uart.port.irqflags	|= irqflag;
> -		ret = serial8250_register_8250_port(&uart);
> -		if (ret < 0) {
> -			dev_err(&dev->dev, "unable to register port at index %d "
> -				"(IO%lx MEM%llx IRQ%d): %d\n", i,
> -				p->iobase, (unsigned long long)p->mapbase,
> -				p->irq, ret);
> -		}
> -	}
> -	return 0;
> -}
> -
> -/*
> - * Remove serial ports registered against a platform device.
> - */
> -static void serial8250_remove(struct platform_device *dev)
> -{
> -	int i;
> -
> -	for (i = 0; i < nr_uarts; i++) {
> -		struct uart_8250_port *up = &serial8250_ports[i];
> -
> -		if (up->port.dev == &dev->dev)
> -			serial8250_unregister_port(i);
> -	}
> -}
> -
> -static int serial8250_suspend(struct platform_device *dev, pm_message_t state)
> -{
> -	int i;
> -
> -	for (i = 0; i < UART_NR; i++) {
> -		struct uart_8250_port *up = &serial8250_ports[i];
> -
> -		if (up->port.type != PORT_UNKNOWN && up->port.dev == &dev->dev)
> -			uart_suspend_port(&serial8250_reg, &up->port);
> -	}
> -
> -	return 0;
> -}
> -
> -static int serial8250_resume(struct platform_device *dev)
> -{
> -	int i;
> -
> -	for (i = 0; i < UART_NR; i++) {
> -		struct uart_8250_port *up = &serial8250_ports[i];
> -
> -		if (up->port.type != PORT_UNKNOWN && up->port.dev == &dev->dev)
> -			serial8250_resume_port(i);
> -	}
> -
> -	return 0;
> -}
> -
> -static struct platform_driver serial8250_isa_driver = {
> -	.probe		= serial8250_probe,
> -	.remove_new	= serial8250_remove,
> -	.suspend	= serial8250_suspend,
> -	.resume		= serial8250_resume,
> -	.driver		= {
> -		.name	= "serial8250",
> -	},
> -};
> -
> -/*
> - * This "device" covers _all_ ISA 8250-compatible serial devices listed
> - * in the table in include/asm/serial.h
> - */
> -static struct platform_device *serial8250_isa_devs;
> -
>  /*
>   * serial8250_register_8250_port and serial8250_unregister_port allows for
>   * 16x50 serial ports to be configured at run-time, to support PCMCIA
> @@ -1110,125 +898,5 @@ void serial8250_unregister_port(int line)
>  }
>  EXPORT_SYMBOL(serial8250_unregister_port);
>  
> -static int __init serial8250_init(void)
> -{
> -	int ret;
> -
> -	if (nr_uarts == 0)
> -		return -ENODEV;
> -
> -	serial8250_isa_init_ports();
> -
> -	pr_info("Serial: 8250/16550 driver, %d ports, IRQ sharing %s\n",
> -		nr_uarts, str_enabled_disabled(share_irqs));
> -
> -#ifdef CONFIG_SPARC
> -	ret = sunserial_register_minors(&serial8250_reg, UART_NR);
> -#else
> -	serial8250_reg.nr = UART_NR;
> -	ret = uart_register_driver(&serial8250_reg);
> -#endif
> -	if (ret)
> -		goto out;
> -
> -	ret = serial8250_pnp_init();
> -	if (ret)
> -		goto unreg_uart_drv;
> -
> -	serial8250_isa_devs = platform_device_alloc("serial8250",
> -						    PLAT8250_DEV_LEGACY);
> -	if (!serial8250_isa_devs) {
> -		ret = -ENOMEM;
> -		goto unreg_pnp;
> -	}
> -
> -	ret = platform_device_add(serial8250_isa_devs);
> -	if (ret)
> -		goto put_dev;
> -
> -	serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);
> -
> -	ret = platform_driver_register(&serial8250_isa_driver);
> -	if (ret == 0)
> -		goto out;
> -
> -	platform_device_del(serial8250_isa_devs);
> -put_dev:
> -	platform_device_put(serial8250_isa_devs);
> -unreg_pnp:
> -	serial8250_pnp_exit();
> -unreg_uart_drv:
> -#ifdef CONFIG_SPARC
> -	sunserial_unregister_minors(&serial8250_reg, UART_NR);
> -#else
> -	uart_unregister_driver(&serial8250_reg);
> -#endif
> -out:
> -	return ret;
> -}
> -
> -static void __exit serial8250_exit(void)
> -{
> -	struct platform_device *isa_dev = serial8250_isa_devs;
> -
> -	/*
> -	 * This tells serial8250_unregister_port() not to re-register
> -	 * the ports (thereby making serial8250_isa_driver permanently
> -	 * in use.)
> -	 */
> -	serial8250_isa_devs = NULL;
> -
> -	platform_driver_unregister(&serial8250_isa_driver);
> -	platform_device_unregister(isa_dev);
> -
> -	serial8250_pnp_exit();
> -
> -#ifdef CONFIG_SPARC
> -	sunserial_unregister_minors(&serial8250_reg, UART_NR);
> -#else
> -	uart_unregister_driver(&serial8250_reg);
> -#endif
> -}
> -
> -module_init(serial8250_init);
> -module_exit(serial8250_exit);
> -
>  MODULE_LICENSE("GPL");
>  MODULE_DESCRIPTION("Generic 8250/16x50 serial driver");
> -
> -module_param_hw(share_irqs, uint, other, 0644);
> -MODULE_PARM_DESC(share_irqs, "Share IRQs with other non-8250/16x50 devices (unsafe)");
> -
> -module_param(nr_uarts, uint, 0644);
> -MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STRING(CONFIG_SERIAL_8250_NR_UARTS) ")");
> -
> -module_param(skip_txen_test, uint, 0644);
> -MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time");
> -
> -MODULE_ALIAS_CHARDEV_MAJOR(TTY_MAJOR);
> -
> -#ifdef CONFIG_SERIAL_8250_DEPRECATED_OPTIONS
> -#ifndef MODULE
> -/* This module was renamed to 8250_core in 3.7.  Keep the old "8250" name
> - * working as well for the module options so we don't break people.  We
> - * need to keep the names identical and the convenient macros will happily
> - * refuse to let us do that by failing the build with redefinition errors
> - * of global variables.  So we stick them inside a dummy function to avoid
> - * those conflicts.  The options still get parsed, and the redefined
> - * MODULE_PARAM_PREFIX lets us keep the "8250." syntax alive.
> - *
> - * This is hacky.  I'm sorry.
> - */
> -static void __used s8250_options(void)
> -{
> -#undef MODULE_PARAM_PREFIX
> -#define MODULE_PARAM_PREFIX "8250_core."
> -
> -	module_param_cb(share_irqs, &param_ops_uint, &share_irqs, 0644);
> -	module_param_cb(nr_uarts, &param_ops_uint, &nr_uarts, 0644);
> -	module_param_cb(skip_txen_test, &param_ops_uint, &skip_txen_test, 0644);
> -}
> -#else
> -MODULE_ALIAS("8250_core");
> -#endif
> -#endif
> diff --git a/drivers/tty/serial/8250/8250_platform.c b/drivers/tty/serial/8250/8250_platform.c
> new file mode 100644
> index 000000000000..ded985182e04
> --- /dev/null
> +++ b/drivers/tty/serial/8250/8250_platform.c
> @@ -0,0 +1,339 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + *  Universal/legacy platform driver for 8250/16550-type serial ports
> + *
> + *  Supports: ISA-compatible 8250/16550 ports
> + *	      PNP 8250/16550 ports
> + *	      "serial8250" platform devices
> + */
> +#include <linux/array_size.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/platform_device.h>
> +
> +#include <linux/serial_8250.h>
> +
> +#ifdef CONFIG_SPARC
> +#include <linux/sunserialcore.h>
> +#endif
> +
> +#include "../serial_base.h"	/* For serial_base_add_isa_preferred_console() */
> +#include "8250.h"
> +
> +/*
> + * Configuration:
> + *    share_irqs   Whether we pass IRQF_SHARED to request_irq().
> + *                 This option is unsafe when used on edge-triggered interrupts.
> + * skip_txen_test  Force skip of txen test at init time.
> + */
> +unsigned int share_irqs = SERIAL8250_SHARE_IRQS;
> +unsigned int skip_txen_test;
> +
> +unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS;
> +
> +#include <asm/serial.h>
> +
> +/*
> + * SERIAL_PORT_DFNS tells us about built-in ports that have no
> + * standard enumeration mechanism. Platforms that can find all
> + * serial ports via mechanisms like ACPI or PCI need not supply it.
> + */
> +#ifndef SERIAL_PORT_DFNS
> +#define SERIAL_PORT_DFNS
> +#endif
> +
> +static const struct old_serial_port old_serial_port[] = {
> +	SERIAL_PORT_DFNS /* defined in asm/serial.h */
> +};
> +
> +serial8250_isa_config_fn serial8250_isa_config;
> +void serial8250_set_isa_configurator(serial8250_isa_config_fn v)
> +{
> +	serial8250_isa_config = v;
> +}
> +EXPORT_SYMBOL(serial8250_set_isa_configurator);
> +
> +void __init serial8250_isa_init_ports(void)
> +{
> +	static int first = 1;
> +	int i, irqflag = 0;
> +
> +	if (!first)
> +		return;
> +	first = 0;
> +
> +	if (nr_uarts > UART_NR)
> +		nr_uarts = UART_NR;
> +
> +	/*
> +	 * Set up initial isa ports based on nr_uart module param, or else
> +	 * default to CONFIG_SERIAL_8250_RUNTIME_UARTS. Note that we do not
> +	 * need to increase nr_uarts when setting up the initial isa ports.
> +	 */
> +	for (i = 0; i < nr_uarts; i++)
> +		serial8250_setup_port(i);
> +
> +	/* chain base port ops to support Remote Supervisor Adapter */
> +	univ8250_port_ops = *univ8250_port_base_ops;
> +	univ8250_rsa_support(&univ8250_port_ops);
> +
> +	if (share_irqs)
> +		irqflag = IRQF_SHARED;
> +
> +	for (i = 0; i < ARRAY_SIZE(old_serial_port) && i < nr_uarts; i++) {
> +		struct uart_8250_port *up = serial8250_get_port(i);
> +		struct uart_port *port = &up->port;
> +
> +		port->iobase   = old_serial_port[i].port;
> +		port->irq      = irq_canonicalize(old_serial_port[i].irq);
> +		port->irqflags = 0;
> +		port->uartclk  = old_serial_port[i].baud_base * 16;
> +		port->flags    = old_serial_port[i].flags;
> +		port->hub6     = 0;
> +		port->membase  = old_serial_port[i].iomem_base;
> +		port->iotype   = old_serial_port[i].io_type;
> +		port->regshift = old_serial_port[i].iomem_reg_shift;
> +
> +		port->irqflags |= irqflag;
> +		if (serial8250_isa_config != NULL)
> +			serial8250_isa_config(i, &up->port, &up->capabilities);
> +
> +		serial_base_add_isa_preferred_console(serial8250_reg.dev_name, i);
> +	}
> +}
> +
> +/*
> + * Register a set of serial devices attached to a platform device.  The
> + * list is terminated with a zero flags entry, which means we expect
> + * all entries to have at least UPF_BOOT_AUTOCONF set.
> + */
> +static int serial8250_probe(struct platform_device *dev)
> +{
> +	struct plat_serial8250_port *p = dev_get_platdata(&dev->dev);

Not related to the change. But..
How is this supposed to work? When serial8250_init creates this ISA
platform device, it doesn't add any platdata. In that case, entire loop
below appears dead code to me. Am I missing something?
 
> +	struct uart_8250_port uart;
> +	int ret, i, irqflag = 0;
> +
> +	memset(&uart, 0, sizeof(uart));
> +
> +	if (share_irqs)
> +		irqflag = IRQF_SHARED;
> +
> +	for (i = 0; p && p->flags != 0; p++, i++) {
> +		uart.port.iobase	= p->iobase;
> +		uart.port.membase	= p->membase;
> +		uart.port.irq		= p->irq;
> +		uart.port.irqflags	= p->irqflags;
> +		uart.port.uartclk	= p->uartclk;
> +		uart.port.regshift	= p->regshift;
> +		uart.port.iotype	= p->iotype;
> +		uart.port.flags		= p->flags;
> +		uart.port.mapbase	= p->mapbase;
> +		uart.port.mapsize	= p->mapsize;
> +		uart.port.hub6		= p->hub6;
> +		uart.port.has_sysrq	= p->has_sysrq;
> +		uart.port.private_data	= p->private_data;
> +		uart.port.type		= p->type;
> +		uart.bugs		= p->bugs;
> +		uart.port.serial_in	= p->serial_in;
> +		uart.port.serial_out	= p->serial_out;
> +		uart.dl_read		= p->dl_read;
> +		uart.dl_write		= p->dl_write;
> +		uart.port.handle_irq	= p->handle_irq;
> +		uart.port.handle_break	= p->handle_break;
> +		uart.port.set_termios	= p->set_termios;
> +		uart.port.set_ldisc	= p->set_ldisc;
> +		uart.port.get_mctrl	= p->get_mctrl;
> +		uart.port.pm		= p->pm;
> +		uart.port.dev		= &dev->dev;
> +		uart.port.irqflags	|= irqflag;
> +		ret = serial8250_register_8250_port(&uart);
> +		if (ret < 0) {
> +			dev_err(&dev->dev, "unable to register port at index %d "
> +				"(IO%lx MEM%llx IRQ%d): %d\n", i,
> +				p->iobase, (unsigned long long)p->mapbase,
> +				p->irq, ret);
> +		}
> +	}
> +	return 0;
> +}
> +
> +/*
> + * Remove serial ports registered against a platform device.
> + */
> +static void serial8250_remove(struct platform_device *dev)
> +{
> +	int i;
> +
> +	for (i = 0; i < nr_uarts; i++) {
> +		struct uart_8250_port *up = serial8250_get_port(i);
> +
> +		if (up->port.dev == &dev->dev)
> +			serial8250_unregister_port(i);
> +	}
> +}
> +
> +static int serial8250_suspend(struct platform_device *dev, pm_message_t state)
> +{
> +	int i;
> +
> +	for (i = 0; i < UART_NR; i++) {
> +		struct uart_8250_port *up = serial8250_get_port(i);
> +
> +		if (up->port.type != PORT_UNKNOWN && up->port.dev == &dev->dev)
> +			uart_suspend_port(&serial8250_reg, &up->port);
> +	}
> +
> +	return 0;
> +}
> +
> +static int serial8250_resume(struct platform_device *dev)
> +{
> +	int i;
> +
> +	for (i = 0; i < UART_NR; i++) {
> +		struct uart_8250_port *up = serial8250_get_port(i);
> +
> +		if (up->port.type != PORT_UNKNOWN && up->port.dev == &dev->dev)
> +			serial8250_resume_port(i);
> +	}
> +
> +	return 0;
> +}
> +
> +static struct platform_driver serial8250_isa_driver = {
> +	.probe		= serial8250_probe,
> +	.remove_new	= serial8250_remove,
> +	.suspend	= serial8250_suspend,
> +	.resume		= serial8250_resume,
> +	.driver		= {
> +		.name	= "serial8250",
> +	},
> +};
> +
> +/*
> + * This "device" covers _all_ ISA 8250-compatible serial devices listed
> + * in the table in include/asm/serial.h
> + */
> +struct platform_device *serial8250_isa_devs;
> +
> +static int __init serial8250_init(void)
> +{
> +	int ret;
> +
> +	if (nr_uarts == 0)
> +		return -ENODEV;
> +
> +	serial8250_isa_init_ports();
> +
> +	pr_info("Serial: 8250/16550 driver, %d ports, IRQ sharing %s\n",
> +		nr_uarts, str_enabled_disabled(share_irqs));
> +
> +#ifdef CONFIG_SPARC
> +	ret = sunserial_register_minors(&serial8250_reg, UART_NR);
> +#else
> +	serial8250_reg.nr = UART_NR;
> +	ret = uart_register_driver(&serial8250_reg);
> +#endif
> +	if (ret)
> +		goto out;
> +
> +	ret = serial8250_pnp_init();
> +	if (ret)
> +		goto unreg_uart_drv;
> +
> +	serial8250_isa_devs = platform_device_alloc("serial8250",
> +						    PLAT8250_DEV_LEGACY);
> +	if (!serial8250_isa_devs) {
> +		ret = -ENOMEM;
> +		goto unreg_pnp;
> +	}
> +
> +	ret = platform_device_add(serial8250_isa_devs);
> +	if (ret)
> +		goto put_dev;
> +
> +	serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);
> +
> +	ret = platform_driver_register(&serial8250_isa_driver);
> +	if (ret == 0)
> +		goto out;
> +
> +	platform_device_del(serial8250_isa_devs);
> +put_dev:
> +	platform_device_put(serial8250_isa_devs);
> +unreg_pnp:
> +	serial8250_pnp_exit();
> +unreg_uart_drv:
> +#ifdef CONFIG_SPARC
> +	sunserial_unregister_minors(&serial8250_reg, UART_NR);
> +#else
> +	uart_unregister_driver(&serial8250_reg);
> +#endif
> +out:
> +	return ret;
> +}
> +module_init(serial8250_init);
> +
> +static void __exit serial8250_exit(void)
> +{
> +	struct platform_device *isa_dev = serial8250_isa_devs;
> +
> +	/*
> +	 * This tells serial8250_unregister_port() not to re-register
> +	 * the ports (thereby making serial8250_isa_driver permanently
> +	 * in use.)
> +	 */
> +	serial8250_isa_devs = NULL;
> +
> +	platform_driver_unregister(&serial8250_isa_driver);
> +	platform_device_unregister(isa_dev);
> +
> +	serial8250_pnp_exit();
> +
> +#ifdef CONFIG_SPARC
> +	sunserial_unregister_minors(&serial8250_reg, UART_NR);
> +#else
> +	uart_unregister_driver(&serial8250_reg);
> +#endif
> +}
> +module_exit(serial8250_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Generic 8250/16x50 serial platform driver");
> +
> +module_param_hw(share_irqs, uint, other, 0644);
> +MODULE_PARM_DESC(share_irqs, "Share IRQs with other non-8250/16x50 devices (unsafe)");
> +
> +module_param(nr_uarts, uint, 0644);
> +MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STRING(CONFIG_SERIAL_8250_NR_UARTS) ")");
> +
> +module_param(skip_txen_test, uint, 0644);
> +MODULE_PARM_DESC(skip_txen_test, "Skip checking for the TXEN bug at init time");
> +
> +MODULE_ALIAS_CHARDEV_MAJOR(TTY_MAJOR);
> +
> +#ifdef CONFIG_SERIAL_8250_DEPRECATED_OPTIONS
> +#ifndef MODULE
> +/* This module was renamed to 8250_core in 3.7.  Keep the old "8250" name
> + * working as well for the module options so we don't break people.  We
> + * need to keep the names identical and the convenient macros will happily
> + * refuse to let us do that by failing the build with redefinition errors
> + * of global variables.  So we stick them inside a dummy function to avoid
> + * those conflicts.  The options still get parsed, and the redefined
> + * MODULE_PARAM_PREFIX lets us keep the "8250." syntax alive.
> + *
> + * This is hacky.  I'm sorry.

Should this comment be updated?

> + */
> +static void __used s8250_options(void)
> +{
> +#undef MODULE_PARAM_PREFIX
> +#define MODULE_PARAM_PREFIX "8250_core."
> +
> +	module_param_cb(share_irqs, &param_ops_uint, &share_irqs, 0644);
> +	module_param_cb(nr_uarts, &param_ops_uint, &nr_uarts, 0644);
> +	module_param_cb(skip_txen_test, &param_ops_uint, &skip_txen_test, 0644);
> +}
> +#else
> +MODULE_ALIAS("8250_core");

Should this be 8250_platform or keeping it same for compatibility reason?

> +#endif
> +#endif
> diff --git a/drivers/tty/serial/8250/Makefile b/drivers/tty/serial/8250/Makefile
> index 96d97184d320..1516de629b61 100644
> --- a/drivers/tty/serial/8250/Makefile
> +++ b/drivers/tty/serial/8250/Makefile
> @@ -3,10 +3,13 @@
>  # Makefile for the 8250 serial device drivers.
>  #
>  
> -obj-$(CONFIG_SERIAL_8250)		+= 8250.o 8250_base.o
> +obj-$(CONFIG_SERIAL_8250)		+= 8250.o
>  8250-y					:= 8250_core.o
> +8250-y					+= 8250_platform.o
>  8250-$(CONFIG_SERIAL_8250_PNP)		+= 8250_pnp.o
>  8250-$(CONFIG_SERIAL_8250_RSA)		+= 8250_rsa.o
> +
> +obj-$(CONFIG_SERIAL_8250)		+= 8250_base.o

Curious to know why this is split?

Acked-by: Sunil V L <sunilvl@ventanamicro.com> 

Thanks,
Sunil
>  8250_base-y				:= 8250_port.o
>  8250_base-$(CONFIG_SERIAL_8250_DMA)	+= 8250_dma.o
>  8250_base-$(CONFIG_SERIAL_8250_DWLIB)	+= 8250_dwlib.o
> -- 
> 2.43.0.rc1.1336.g36b5255a03ac
>

Thu, May 09, 2024 at 10:51:11AM +0530, Sunil V L kirjoitti:

> Many thanks for helping with this!. Just few questions below for my
> understanding.

You are welcome! Meanwhile, can you test these changes?

> On Mon, May 06, 2024 at 05:00:59PM +0300, Andy Shevchenko wrote:

...

> > +void __init serial8250_isa_init_ports(void)
> > +{
> > +	static int first = 1;
> > +	int i, irqflag = 0;
> > +
> > +	if (!first)
> > +		return;
> > +	first = 0;
> > +
> > +	if (nr_uarts > UART_NR)
> > +		nr_uarts = UART_NR;
> > +
> > +	/*
> > +	 * Set up initial isa ports based on nr_uart module param, or else
> > +	 * default to CONFIG_SERIAL_8250_RUNTIME_UARTS. Note that we do not
> > +	 * need to increase nr_uarts when setting up the initial isa ports.
> > +	 */
> > +	for (i = 0; i < nr_uarts; i++)
> > +		serial8250_setup_port(i);
> > +
> > +	/* chain base port ops to support Remote Supervisor Adapter */
> > +	univ8250_port_ops = *univ8250_port_base_ops;
> > +	univ8250_rsa_support(&univ8250_port_ops);
> > +
> > +	if (share_irqs)
> > +		irqflag = IRQF_SHARED;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(old_serial_port) && i < nr_uarts; i++) {
> > +		struct uart_8250_port *up = serial8250_get_port(i);
> > +		struct uart_port *port = &up->port;
> > +
> > +		port->iobase   = old_serial_port[i].port;
> > +		port->irq      = irq_canonicalize(old_serial_port[i].irq);
> > +		port->irqflags = 0;
> > +		port->uartclk  = old_serial_port[i].baud_base * 16;
> > +		port->flags    = old_serial_port[i].flags;
> > +		port->hub6     = 0;
> > +		port->membase  = old_serial_port[i].iomem_base;
> > +		port->iotype   = old_serial_port[i].io_type;
> > +		port->regshift = old_serial_port[i].iomem_reg_shift;
> > +
> > +		port->irqflags |= irqflag;
> > +		if (serial8250_isa_config != NULL)
> > +			serial8250_isa_config(i, &up->port, &up->capabilities);
> > +
> > +		serial_base_add_isa_preferred_console(serial8250_reg.dev_name, i);
> > +	}
> > +}
> > +
> > +/*
> > + * Register a set of serial devices attached to a platform device.  The
> > + * list is terminated with a zero flags entry, which means we expect
> > + * all entries to have at least UPF_BOOT_AUTOCONF set.
> > + */
> > +static int serial8250_probe(struct platform_device *dev)
> > +{
> > +	struct plat_serial8250_port *p = dev_get_platdata(&dev->dev);

> Not related to the change. But..
> How is this supposed to work? When serial8250_init creates this ISA
> platform device,
> it doesn't add any platdata. In that case, entire loop
> below appears dead code to me. Am I missing something?

Yes, you are. Here is the answer:
https://elixir.bootlin.com/linux/latest/C/ident/plat_serial8250_port

I.o.w. it depends on the platform and actual drivers that instantiate the
serial8250 platform device. You found only one case for which it's a dead
code, but not for many others.

> > +	struct uart_8250_port uart;
> > +	int ret, i, irqflag = 0;
> > +
> > +	memset(&uart, 0, sizeof(uart));
> > +
> > +	if (share_irqs)
> > +		irqflag = IRQF_SHARED;
> > +
> > +	for (i = 0; p && p->flags != 0; p++, i++) {
> > +		uart.port.iobase	= p->iobase;
> > +		uart.port.membase	= p->membase;
> > +		uart.port.irq		= p->irq;
> > +		uart.port.irqflags	= p->irqflags;
> > +		uart.port.uartclk	= p->uartclk;
> > +		uart.port.regshift	= p->regshift;
> > +		uart.port.iotype	= p->iotype;
> > +		uart.port.flags		= p->flags;
> > +		uart.port.mapbase	= p->mapbase;
> > +		uart.port.mapsize	= p->mapsize;
> > +		uart.port.hub6		= p->hub6;
> > +		uart.port.has_sysrq	= p->has_sysrq;
> > +		uart.port.private_data	= p->private_data;
> > +		uart.port.type		= p->type;
> > +		uart.bugs		= p->bugs;
> > +		uart.port.serial_in	= p->serial_in;
> > +		uart.port.serial_out	= p->serial_out;
> > +		uart.dl_read		= p->dl_read;
> > +		uart.dl_write		= p->dl_write;
> > +		uart.port.handle_irq	= p->handle_irq;
> > +		uart.port.handle_break	= p->handle_break;
> > +		uart.port.set_termios	= p->set_termios;
> > +		uart.port.set_ldisc	= p->set_ldisc;
> > +		uart.port.get_mctrl	= p->get_mctrl;
> > +		uart.port.pm		= p->pm;
> > +		uart.port.dev		= &dev->dev;
> > +		uart.port.irqflags	|= irqflag;
> > +		ret = serial8250_register_8250_port(&uart);
> > +		if (ret < 0) {
> > +			dev_err(&dev->dev, "unable to register port at index %d "
> > +				"(IO%lx MEM%llx IRQ%d): %d\n", i,
> > +				p->iobase, (unsigned long long)p->mapbase,
> > +				p->irq, ret);
> > +		}
> > +	}
> > +	return 0;
> > +}

> > +static struct platform_driver serial8250_isa_driver = {
> > +	.probe		= serial8250_probe,
> > +	.remove_new	= serial8250_remove,
> > +	.suspend	= serial8250_suspend,
> > +	.resume		= serial8250_resume,
> > +	.driver		= {
> > +		.name	= "serial8250",
> > +	},
> > +};
> > +
> > +/*
> > + * This "device" covers _all_ ISA 8250-compatible serial devices listed
> > + * in the table in include/asm/serial.h
> > + */
> > +struct platform_device *serial8250_isa_devs;
> > +
> > +static int __init serial8250_init(void)
> > +{
> > +	int ret;
> > +
> > +	if (nr_uarts == 0)
> > +		return -ENODEV;
> > +
> > +	serial8250_isa_init_ports();
> > +
> > +	pr_info("Serial: 8250/16550 driver, %d ports, IRQ sharing %s\n",
> > +		nr_uarts, str_enabled_disabled(share_irqs));
> > +
> > +#ifdef CONFIG_SPARC
> > +	ret = sunserial_register_minors(&serial8250_reg, UART_NR);
> > +#else
> > +	serial8250_reg.nr = UART_NR;
> > +	ret = uart_register_driver(&serial8250_reg);
> > +#endif
> > +	if (ret)
> > +		goto out;
> > +
> > +	ret = serial8250_pnp_init();
> > +	if (ret)
> > +		goto unreg_uart_drv;
> > +
> > +	serial8250_isa_devs = platform_device_alloc("serial8250",
> > +						    PLAT8250_DEV_LEGACY);
> > +	if (!serial8250_isa_devs) {
> > +		ret = -ENOMEM;
> > +		goto unreg_pnp;
> > +	}
> > +
> > +	ret = platform_device_add(serial8250_isa_devs);
> > +	if (ret)
> > +		goto put_dev;
> > +
> > +	serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);
> > +
> > +	ret = platform_driver_register(&serial8250_isa_driver);
> > +	if (ret == 0)
> > +		goto out;
> > +
> > +	platform_device_del(serial8250_isa_devs);
> > +put_dev:
> > +	platform_device_put(serial8250_isa_devs);
> > +unreg_pnp:
> > +	serial8250_pnp_exit();
> > +unreg_uart_drv:
> > +#ifdef CONFIG_SPARC
> > +	sunserial_unregister_minors(&serial8250_reg, UART_NR);
> > +#else
> > +	uart_unregister_driver(&serial8250_reg);
> > +#endif
> > +out:
> > +	return ret;
> > +}
> > +module_init(serial8250_init);

...

> > +#ifdef CONFIG_SERIAL_8250_DEPRECATED_OPTIONS
> > +#ifndef MODULE
> > +/* This module was renamed to 8250_core in 3.7.  Keep the old "8250" name
> > + * working as well for the module options so we don't break people.  We
> > + * need to keep the names identical and the convenient macros will happily
> > + * refuse to let us do that by failing the build with redefinition errors
> > + * of global variables.  So we stick them inside a dummy function to avoid
> > + * those conflicts.  The options still get parsed, and the redefined
> > + * MODULE_PARAM_PREFIX lets us keep the "8250." syntax alive.
> > + *
> > + * This is hacky.  I'm sorry.
> 
> Should this comment be updated?

Why? There is no change in this approach. It stays as it was.

> > + */
> > +static void __used s8250_options(void)
> > +{
> > +#undef MODULE_PARAM_PREFIX
> > +#define MODULE_PARAM_PREFIX "8250_core."
> > +
> > +	module_param_cb(share_irqs, &param_ops_uint, &share_irqs, 0644);
> > +	module_param_cb(nr_uarts, &param_ops_uint, &nr_uarts, 0644);
> > +	module_param_cb(skip_txen_test, &param_ops_uint, &skip_txen_test, 0644);
> > +}
> > +#else
> > +MODULE_ALIAS("8250_core");
> 
> Should this be 8250_platform or keeping it same for compatibility reason?

No. The module name is still 8250_core if you carefully check the Makefile.

> > +#endif
> > +#endif

...

> > -obj-$(CONFIG_SERIAL_8250)		+= 8250.o 8250_base.o
> > +obj-$(CONFIG_SERIAL_8250)		+= 8250.o
> >  8250-y					:= 8250_core.o
> > +8250-y					+= 8250_platform.o
> >  8250-$(CONFIG_SERIAL_8250_PNP)		+= 8250_pnp.o
> >  8250-$(CONFIG_SERIAL_8250_RSA)		+= 8250_rsa.o
> > +
> > +obj-$(CONFIG_SERIAL_8250)		+= 8250_base.o
> 
> Curious to know why this is split?

The line

obj-$(X) += foo.o bar.o

means that if X=m, the foo and bar will be separate modules. Since we have a
few object files per each of them it's better to split them in Makefile in
order to have better readability and maintenance. It's pure done for these
purposes.

> Acked-by: Sunil V L <sunilvl@ventanamicro.com> 

Thank you, but I would prefer Tested-by as it is kinda intrusive change.
I tested it on Intel hardware but it might have (hidden) issues on other
setups.

> >  8250_base-y				:= 8250_port.o
> >  8250_base-$(CONFIG_SERIAL_8250_DMA)	+= 8250_dma.o
> >  8250_base-$(CONFIG_SERIAL_8250_DWLIB)	+= 8250_dwlib.o

On Thu, May 09, 2024 at 04:49:51PM +0300, Andy Shevchenko wrote:
> Thu, May 09, 2024 at 10:51:11AM +0530, Sunil V L kirjoitti:
> 
> > Many thanks for helping with this!. Just few questions below for my
> > understanding.
> 
> You are welcome! Meanwhile, can you test these changes?
> 
Hi Andy,

Sorry for delayed response. For some reason, it landed in spam and I
missed it. Thanks a lot for the clarifications!

Tested this on RISC-V and works well.

Tested-by: Sunil V L <sunilvl@ventanamicro.com>

Thanks,
Sunil