[RFC,v2,2/3] ACPI: Add support for Platform Communication Channel

diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index fc133d4..d8aa613 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -74,7 +74,7 @@  obj-$(CONFIG_ACPI_HED)		+= hed.o
 obj-$(CONFIG_ACPI_EC_DEBUGFS)	+= ec_sys.o
 obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o
 obj-$(CONFIG_ACPI_BGRT)		+= bgrt.o
-
+obj-$(CONFIG_ACPI_PCC)		+= pcc.o
 # processor has its own "processor." module_param namespace
 processor-y			:= processor_driver.o processor_throttling.o
 processor-y			+= processor_idle.o processor_thermal.o
diff --git a/drivers/acpi/pcc.c b/drivers/acpi/pcc.c
new file mode 100644
index 0000000..b93a8e7
--- /dev/null
+++ b/drivers/acpi/pcc.c
@@ -0,0 +1,225 @@ 
+/*
+ *	Copyright (C) 2014 Linaro Ltd.
+ *	Author:	Ashwin Chaugule <ashwin.chaugule@linaro.org>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+#include <linux/ioctl.h>
+#include <linux/vmalloc.h>
+#include <linux/mailbox_controller.h>
+
+#include <acpi/actbl.h>
+
+#define MAX_PCC_SUBSPACES	256
+#define PCCS_SS_SIG_MAGIC	0x50434300
+#define PCC_CMD_COMPLETE	0x1
+#define PCC_VERSION			"0.1"
+
+struct mbox_chan pcc_mbox_chan[MAX_PCC_SUBSPACES];
+
+static bool pcc_tx_done(struct mbox_chan *chan)
+{
+	struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
+	struct acpi_pcct_shared_memory *generic_comm_base =
+		(struct acpi_pcct_shared_memory *) pcct_ss->base_address;
+	u16 cmd_delay = pcct_ss->min_turnaround_time;
+
+	/* Wait for Platform to consume. */
+	while (!(ioread16(&generic_comm_base->status) & PCC_CMD_COMPLETE))
+		udelay(cmd_delay);
+
+	return true;
+}
+
+/* Channel lock is already held by mbox controller code. */
+static int pcc_send_data(struct mbox_chan *chan, void *data)
+{
+	struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
+	struct acpi_pcct_shared_memory *generic_comm_base =
+		(struct acpi_pcct_shared_memory *) pcct_ss->base_address;
+	struct acpi_generic_address doorbell;
+	u64 doorbell_preserve;
+	u64 doorbell_val;
+	u64 doorbell_write;
+	u16 cmd = 0;
+	u16 ss_idx = 0;
+	int ret = 0;
+
+	/*
+	 * Min time in usec that OSPM is expected to wait
+	 * before sending the next PCC cmd.
+	 */
+	u16 cmd_delay = pcct_ss->min_turnaround_time;
+
+	/* Get PCC CMD */
+	ret = kstrtou16((char*)data, 0, &cmd);
+	if (ret < 0) {
+		pr_err("Err while converting PCC CMD to u16: %d\n", ret);
+		goto out_err;
+	}
+
+	/* Get PCC Subspace ID */
+	ret = kstrtou16(chan->name, 0, &ss_idx);
+	if (ret < 0) {
+		pr_err("Err while converting PCC ss_idx to u16: %d\n", ret);
+		goto out_err;
+	}
+
+	doorbell = pcct_ss->doorbell_register;
+	doorbell_preserve = pcct_ss->preserve_mask;
+	doorbell_write = pcct_ss->write_mask;
+
+	/* Loop until CMD complete bit is set. For prev cmds. */
+	while (!(ioread16(&generic_comm_base->status) & PCC_CMD_COMPLETE))
+		udelay(cmd_delay);
+
+	/* Write to the shared comm region. */
+	iowrite16(cmd, &generic_comm_base->command);
+
+	/* Write Subspace MAGIC value so platform can identify destination. */
+	iowrite32((PCCS_SS_SIG_MAGIC | ss_idx), &generic_comm_base->signature);
+
+	/* Flip CMD COMPLETE bit */
+	iowrite16(0, &generic_comm_base->status);
+
+	/* Sync notification from OSPM to Platform. */
+	acpi_read(&doorbell_val, &doorbell);
+	acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
+			&doorbell);
+
+out_err:
+	return ret;
+}
+
+static int pcc_chan_startup(struct mbox_chan *chan)
+{
+	return 0;
+}
+
+static void pcc_chan_shutdown(struct mbox_chan *chan)
+{
+	return;
+}
+
+static struct mbox_controller pcc_mbox_ctrl = {};
+
+static struct mbox_chan_ops pcc_chan_ops = {
+	.send_data	=	pcc_send_data,
+	.startup	=	pcc_chan_startup,
+	.shutdown	=	pcc_chan_shutdown,
+	.last_tx_done	=	pcc_tx_done,
+};
+
+static int parse_pcc_subspace(struct acpi_subtable_header *header,
+		const unsigned long end)
+{
+	struct acpi_pcct_subspace *pcct_ss;
+	char *chan_name;
+
+	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
+		pcct_ss = (struct acpi_pcct_subspace *) header;
+
+		if (pcct_ss->header.type != ACPI_PCCT_TYPE_GENERIC_SUBSPACE) {
+			pr_err("Incorrect PCC Subspace type detected\n");
+			return -EINVAL;
+		}
+
+		/* New mbox channel entry for each PCC subspace detected. */
+		pcc_mbox_chan[pcc_mbox_ctrl.num_chans].con_priv = pcct_ss;
+
+		/* Use the PCC subspace ID as the channel name. */
+		chan_name = (char *)kmalloc(sizeof(short), GFP_KERNEL);
+		if (!chan_name) {
+			pr_err("No mem for channel name\n");
+			return -ENOSPC;
+		}
+
+		pcc_mbox_chan[pcc_mbox_ctrl.num_chans].name = chan_name;
+		snprintf(pcc_mbox_chan[pcc_mbox_ctrl.num_chans].name,
+				sizeof(short), "%d", pcc_mbox_ctrl.num_chans);
+
+		pcc_mbox_ctrl.num_chans++;
+
+	} else {
+		pr_err("No more space for PCC subspaces.\n");
+		return -ENOSPC;
+	}
+
+	return 0;
+}
+
+static int __init pcc_probe(void)
+{
+	acpi_status status = AE_OK;
+	acpi_size pcct_tbl_header_size;
+	struct acpi_table_pcct *pcct_tbl;
+
+	/* Search for PCCT */
+	status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0,
+			(struct acpi_table_header **)&pcct_tbl,
+			&pcct_tbl_header_size);
+
+	if (ACPI_SUCCESS(status) && !pcct_tbl) {
+		pr_warn("PCCT header not found.\n");
+		status = AE_NOT_FOUND;
+		goto out_err;
+	}
+
+	status = acpi_table_parse_entries(ACPI_SIG_PCCT,
+			sizeof(struct acpi_table_pcct),
+			ACPI_PCCT_TYPE_GENERIC_SUBSPACE,
+			parse_pcc_subspace, MAX_PCC_SUBSPACES);
+
+	if (ACPI_SUCCESS(status))
+		pr_err("Error parsing PCC subspaces from PCCT\n");
+
+	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
+
+	pcc_mbox_ctrl.chans = pcc_mbox_chan;
+	pcc_mbox_ctrl.ops = &pcc_chan_ops;
+	pcc_mbox_ctrl.name = "PCCT";
+	pcc_mbox_ctrl.txdone_poll = true;
+	pcc_mbox_ctrl.txpoll_period = 1;
+
+	pr_info("Registering PCC driver as mbox controller\n");
+	mbox_controller_register(&pcc_mbox_ctrl);
+
+out_err:
+	return ACPI_SUCCESS(status) ? 1 : 0;
+}
+
+static int __init pcc_init(void)
+{
+	int ret;
+
+	if (acpi_disabled)
+		return -ENODEV;
+
+	/* Check if PCC support is available. */
+	ret = pcc_probe();
+
+	if (ret) {
+		pr_debug("PCC probe failed.\n");
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+device_initcall(pcc_init);
diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index c8b5c13..7aea896 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -50,4 +50,15 @@  config OMAP_MBOX_KFIFO_SIZE
 	  Specify the default size of mailbox's kfifo buffers (bytes).
 	  This can also be changed at runtime (via the mbox_kfifo_size
 	  module parameter).
+
+config ACPI_PCC
+	bool "ACPI Platform Communication Channel"
+	def_bool n
+	depends on ACPI
+	help
+	Enable this option if your platform supports PCC as defined in the
+	ACPI spec 5.0a+. PCC is a generic mechanism for the OS to communicate
+	with a platform such as a BMC. PCC is typically used by CPPC, RAS
+	and MPST.
+
 endif