linux-kernel - [PATCH v2 4/7] serial: qcom-geni: fix receiver enable

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Message-ID: <20241001125033.10625-5-johan+linaro@kernel.org>
Date: Tue,  1 Oct 2024 14:50:30 +0200
From: Johan Hovold <johan+linaro@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org,
	Johan Hovold <johan+linaro@...nel.org>,
	stable@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH v2 4/7] serial: qcom-geni: fix receiver enable

The receiver should be enabled in the startup() callback and there is no
need to stop it on every termios update.

Since commit 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during
console writes") the calls to manipulate the secondary interrupts, which
were done without holding the port lock, can lead to the receiver being
left disabled when set_termios() races with the console code (e.g. when
init opens the tty during boot).

The calls to stop and start rx in set_termios() can similarly race with
DMA completion and, for example, cause the DMA buffer to be unmapped
twice or the mapping to be leaked.

Fixes: 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during console writes")
Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA")
Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP")
Cc: stable@...r.kernel.org      # 6.3
Cc: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index dea688db0d7c..5b6c5388efee 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1179,6 +1179,11 @@ static int qcom_geni_serial_startup(struct uart_port *uport)
 		if (ret)
 			return ret;
 	}
+
+	uart_port_lock_irq(uport);
+	qcom_geni_serial_start_rx(uport);
+	uart_port_unlock_irq(uport);
+
 	enable_irq(uport->irq);
 
 	return 0;
@@ -1264,7 +1269,6 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
 	unsigned int avg_bw_core;
 	unsigned long timeout;
 
-	qcom_geni_serial_stop_rx(uport);
 	/* baud rate */
 	baud = uart_get_baud_rate(uport, termios, old, 300, 4000000);
 
@@ -1280,7 +1284,7 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
 		dev_err(port->se.dev,
 			"Couldn't find suitable clock rate for %u\n",
 			baud * sampling_rate);
-		goto out_restart_rx;
+		return;
 	}
 
 	dev_dbg(port->se.dev, "desired_rate = %u, clk_rate = %lu, clk_div = %u\n",
@@ -1371,8 +1375,6 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
 	writel(stop_bit_len, uport->membase + SE_UART_TX_STOP_BIT_LEN);
 	writel(ser_clk_cfg, uport->membase + GENI_SER_M_CLK_CFG);
 	writel(ser_clk_cfg, uport->membase + GENI_SER_S_CLK_CFG);
-out_restart_rx:
-	qcom_geni_serial_start_rx(uport);
 }
 
 #ifdef CONFIG_SERIAL_QCOM_GENI_CONSOLE
-- 
2.45.2