From patchwork Fri Dec 6 19:30:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miroslav Ondra via B4 Relay X-Patchwork-Id: 848416 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0ADC2203D51; Fri, 6 Dec 2024 19:30:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733513406; cv=none; b=TKzRBBeXN1rDOWMtRmv+izOIxt0yZApghbUR3BVClbnKecP9SNyCOramzEhgPxoDNLsCOjwSgPXTWrb0UgHPn5J5l+yl3AmgzTZiqINTxpRpIoYSwjGECVnphzQsblp3PSW4x3RmATQicB4/0Pkcp9EYGFCrb2cDP24lFKNrKKY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733513406; c=relaxed/simple; bh=9VtPqJ3ixJqBOlJgjri8TnxU58OVb+Ya1hK3sseea/I=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:To:Cc; b=nQ+syJUGedKELbpgpjfCXXpPKSY5eQeviFN6NREsf7kYyugkwx+MVBK5EzyKL5Lyrse3ihP3YMDMRN+YKWj141Y4B4T2Ut4SBvyXKj46oR4erGuOJ2UqoxOG+cMo39/eieIx/Ex0O/Wt14KWXkKWxAyWBpkXlj11QfFvJwgJ+o0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VPd6gFcj; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VPd6gFcj" Received: by smtp.kernel.org (Postfix) with ESMTPS id 6AB31C4CED1; Fri, 6 Dec 2024 19:30:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1733513405; bh=9VtPqJ3ixJqBOlJgjri8TnxU58OVb+Ya1hK3sseea/I=; h=From:Date:Subject:To:Cc:Reply-To:From; b=VPd6gFcjWDctDZIM4DDC3sjXGgpCeEp2SGu6iRX4MEiRRuy27vziTVI/YR2ZMO45f JHhh4Q1uJGXNC5muw4NwLJg7MbZetr7WwgvKUwHpiZrTFU6EQNMtBbjF1UM8DAEuoF fTBOszLRQ7RNqUGCjwpN+BSIeAAs11tNHmPStxyC/E1ieHih+Mf5/JugNXWPXeKV8X GO2kihnST2hVgIlmKTym8mAgzpKkRHaZLVVVEr2BzZAkURoVe6a6imS9k2q43UBQFT fVgRBnu5AXFpj2l7BbPmk2A0GIzGEh+VmSJi87hnb9pb7yxc5XJLEqvXrVGcz2rfwC RKGv3lE5BUuDg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5ED7CE7717B; Fri, 6 Dec 2024 19:30:05 +0000 (UTC) From: Miroslav Ondra via B4 Relay Date: Fri, 06 Dec 2024 20:30:03 +0100 Subject: [PATCH v2] serial: amba-pl011: Fix RTS handling in RS485 mode Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20241206-master-v2-1-02628dc036c9@faster.cz> X-B4-Tracking: v=1; b=H4sIALpQU2cC/zXMwQ6CMAzG8VchPTuzlgaDJ9/DcFigkx4Es5FFJ Xt356LHf/vlt0OUoBLh3OwQJGnUdSlBhwbG2S03MTqVBrLEiHgydxc3CaafvOWWPYplKONHEK/ PCl2H0rPGbQ2v6ib8Xn8EtX8ioUFDncWemTpx7cXXx3F8w5Bz/gA1BKgNnAAAAA== X-Change-ID: 20241117-master-9df0434f1e04 To: Russell King , Greg Kroah-Hartman , Jiri Slaby , Lino Sanfilippo Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, Miroslav Ondra X-Mailer: b4 0.14.2 X-Developer-Signature: v=1; a=ed25519-sha256; t=1733513404; l=8545; i=ondra@faster.cz; s=20241119; h=from:subject:message-id; bh=zUbG+524WMk+txIM0uzH00Uwjez0DoZnVYi123HLrvU=; b=BHjqF6XuAROw2mv2gxdnGAtJVe0B6QcnYn9MoeTgA+XA43omni+6cfzeax87pnn7nqFDaA9j3 K2RYEtgaACwCPGmOMmheJtk/EquEdtFmf9/V1+wPdlA5FUqGN8tcPVP X-Developer-Key: i=ondra@faster.cz; a=ed25519; pk=OgmjYvFJ0npSTnp6LOgY/siJeZ/6t3nOEs4jE9vm0Oc= X-Endpoint-Received: by B4 Relay for ondra@faster.cz/20241119 with auth_id=282 X-Original-From: Miroslav Ondra Reply-To: ondra@faster.cz From: Miroslav Ondra Data loss on serial line was observed during communication through serial ports ttyAMA1 and ttyAMA2 interconnected via RS485 transcievers. Both ports are in one BCM2711 (Compute Module CM40) and they share the same interrupt line. The problem is caused by long waiting for tx queue flush in the function pl011_rs485_tx_stop. Udelay or mdelay are used to wait. The function is called from the interrupt handler. If multiple devices share a single interrupt line, late processing of pending interrupts and data loss may occur. When operation of both devices are synchronous, collisions are quite often. This rework is based on the method used in tty/serial/imx.c Use hrtimer instead of udelay and mdelay calls. Replace simple bool variable rs485_tx_started by 4-state variable rs485_tx_state. Signed-off-by: Miroslav Ondra Tested-by: Lino Sanfilippo --- Thanks Greg for the advice. --- Changes in v2: - Reword commit message to explain the problem. - Link to v1: https://lore.kernel.org/r/20241123-master-v1-1-260194426ea3@faster.cz --- drivers/tty/serial/amba-pl011.c | 126 ++++++++++++++++++++++++++++++---------- 1 file changed, 96 insertions(+), 30 deletions(-) --- base-commit: cfba9f07a1d6aeca38f47f1f472cfb0ba133d341 change-id: 20241117-master-9df0434f1e04 Best regards, diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 69b7a3e1e418e200944b0b0429b6341d71ecff26..04212c823a91d5a343327292d8ffd95be1465473 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -248,6 +248,13 @@ struct pl011_dmatx_data { bool queued; }; +enum pl011_rs485_tx_state { + OFF, + WAIT_AFTER_RTS, + SEND, + WAIT_AFTER_SEND, +}; + /* * We wrap our port structure around the generic uart_port. */ @@ -261,8 +268,10 @@ struct uart_amba_port { unsigned int fifosize; /* vendor-specific */ unsigned int fixed_baud; /* vendor-set fixed baud rate */ char type[12]; - bool rs485_tx_started; - unsigned int rs485_tx_drain_interval; /* usecs */ + ktime_t rs485_tx_drain_interval; /* nano */ + enum pl011_rs485_tx_state rs485_tx_state; + struct hrtimer trigger_start_tx; + struct hrtimer trigger_stop_tx; #ifdef CONFIG_DMA_ENGINE /* DMA stuff */ unsigned int dmacr; /* dma control reg */ @@ -1260,30 +1269,31 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap) static void pl011_rs485_tx_stop(struct uart_amba_port *uap) { - /* - * To be on the safe side only time out after twice as many iterations - * as fifo size. - */ - const int MAX_TX_DRAIN_ITERS = uap->port.fifosize * 2; struct uart_port *port = &uap->port; - int i = 0; u32 cr; - /* Wait until hardware tx queue is empty */ - while (!pl011_tx_empty(port)) { - if (i > MAX_TX_DRAIN_ITERS) { - dev_warn(port->dev, - "timeout while draining hardware tx queue\n"); - break; - } + if (uap->rs485_tx_state == SEND) + uap->rs485_tx_state = WAIT_AFTER_SEND; - udelay(uap->rs485_tx_drain_interval); - i++; + if (uap->rs485_tx_state == WAIT_AFTER_SEND) { + /* Schedule hrtimer if tx queue not empty */ + if (!pl011_tx_empty(port)) { + hrtimer_start(&uap->trigger_stop_tx, + uap->rs485_tx_drain_interval, + HRTIMER_MODE_REL); + return; + } + if (port->rs485.delay_rts_after_send > 0) { + hrtimer_start(&uap->trigger_stop_tx, + ms_to_ktime(port->rs485.delay_rts_after_send), + HRTIMER_MODE_REL); + return; + } + /* Continue without any delay */ + } else if (uap->rs485_tx_state == WAIT_AFTER_RTS) { + hrtimer_try_to_cancel(&uap->trigger_start_tx); } - if (port->rs485.delay_rts_after_send) - mdelay(port->rs485.delay_rts_after_send); - cr = pl011_read(uap, REG_CR); if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND) @@ -1296,7 +1306,7 @@ static void pl011_rs485_tx_stop(struct uart_amba_port *uap) cr |= UART011_CR_RXE; pl011_write(cr, uap, REG_CR); - uap->rs485_tx_started = false; + uap->rs485_tx_state = OFF; } static void pl011_stop_tx(struct uart_port *port) @@ -1304,11 +1314,18 @@ static void pl011_stop_tx(struct uart_port *port) struct uart_amba_port *uap = container_of(port, struct uart_amba_port, port); + if (port->rs485.flags & SER_RS485_ENABLED && + uap->rs485_tx_state == WAIT_AFTER_RTS) { + pl011_rs485_tx_stop(uap); + return; + } + uap->im &= ~UART011_TXIM; pl011_write(uap->im, uap, REG_IMSC); pl011_dma_tx_stop(uap); - if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started) + if (port->rs485.flags & SER_RS485_ENABLED && + uap->rs485_tx_state != OFF) pl011_rs485_tx_stop(uap); } @@ -1328,10 +1345,19 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap) struct uart_port *port = &uap->port; u32 cr; + if (uap->rs485_tx_state == WAIT_AFTER_RTS) { + uap->rs485_tx_state = SEND; + return; + } + if (uap->rs485_tx_state == WAIT_AFTER_SEND) { + hrtimer_try_to_cancel(&uap->trigger_stop_tx); + uap->rs485_tx_state = SEND; + return; + } + /* uap->rs485_tx_state == OFF */ /* Enable transmitter */ cr = pl011_read(uap, REG_CR); cr |= UART011_CR_TXE; - /* Disable receiver if half-duplex */ if (!(port->rs485.flags & SER_RS485_RX_DURING_TX)) cr &= ~UART011_CR_RXE; @@ -1343,10 +1369,14 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap) pl011_write(cr, uap, REG_CR); - if (port->rs485.delay_rts_before_send) - mdelay(port->rs485.delay_rts_before_send); - - uap->rs485_tx_started = true; + if (port->rs485.delay_rts_before_send > 0) { + uap->rs485_tx_state = WAIT_AFTER_RTS; + hrtimer_start(&uap->trigger_start_tx, + ms_to_ktime(port->rs485.delay_rts_before_send), + HRTIMER_MODE_REL); + } else { + uap->rs485_tx_state = SEND; + } } static void pl011_start_tx(struct uart_port *port) @@ -1355,13 +1385,44 @@ static void pl011_start_tx(struct uart_port *port) container_of(port, struct uart_amba_port, port); if ((uap->port.rs485.flags & SER_RS485_ENABLED) && - !uap->rs485_tx_started) + uap->rs485_tx_state != SEND) { pl011_rs485_tx_start(uap); + if (uap->rs485_tx_state == WAIT_AFTER_RTS) + return; + } if (!pl011_dma_tx_start(uap)) pl011_start_tx_pio(uap); } +static enum hrtimer_restart pl011_trigger_start_tx(struct hrtimer *t) +{ + struct uart_amba_port *uap = + container_of(t, struct uart_amba_port, trigger_start_tx); + unsigned long flags; + + uart_port_lock_irqsave(&uap->port, &flags); + if (uap->rs485_tx_state == WAIT_AFTER_RTS) + pl011_start_tx(&uap->port); + uart_port_unlock_irqrestore(&uap->port, flags); + + return HRTIMER_NORESTART; +} + +static enum hrtimer_restart pl011_trigger_stop_tx(struct hrtimer *t) +{ + struct uart_amba_port *uap = + container_of(t, struct uart_amba_port, trigger_stop_tx); + unsigned long flags; + + uart_port_lock_irqsave(&uap->port, &flags); + if (uap->rs485_tx_state == WAIT_AFTER_SEND) + pl011_rs485_tx_stop(uap); + uart_port_unlock_irqrestore(&uap->port, flags); + + return HRTIMER_NORESTART; +} + static void pl011_stop_rx(struct uart_port *port) { struct uart_amba_port *uap = @@ -1953,7 +2014,7 @@ static void pl011_shutdown(struct uart_port *port) pl011_dma_shutdown(uap); - if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started) + if ((port->rs485.flags & SER_RS485_ENABLED && uap->rs485_tx_state != OFF)) pl011_rs485_tx_stop(uap); free_irq(uap->port.irq, uap); @@ -2098,7 +2159,7 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios, * with the given baud rate. We use this as the poll interval when we * wait for the tx queue to empty. */ - uap->rs485_tx_drain_interval = DIV_ROUND_UP(bits * 1000 * 1000, baud); + uap->rs485_tx_drain_interval = ns_to_ktime(DIV_ROUND_UP(bits * NSEC_PER_SEC, baud)); pl011_setup_status_masks(port, termios); @@ -2807,6 +2868,11 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) } } + hrtimer_init(&uap->trigger_start_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init(&uap->trigger_stop_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + uap->trigger_start_tx.function = pl011_trigger_start_tx; + uap->trigger_stop_tx.function = pl011_trigger_stop_tx; + ret = pl011_setup_port(&dev->dev, uap, &dev->res, portnr); if (ret) return ret;