[PATCH] serial: fsl_lpuart: Reset prior to registration

[PATCH] serial: fsl_lpuart: Reset prior to registration

[Lukas Wunner]

Since commit bd5305dcabbc ("tty: serial: fsl_lpuart: do software reset
for imx7ulp and imx8qxp"), certain i.MX UARTs are reset after they've
already been registered.  Register state may thus be clobbered after
user space has begun to open and access the UART.

Avoid by performing the reset prior to registration.

Fixes: bd5305dcabbc ("tty: serial: fsl_lpuart: do software reset for imx7ulp and imx8qxp")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: stable@vger.kernel.org # v5.15+
Cc: Fugang Duan <fugang.duan@nxp.com>
Cc: Sherry Sun <sherry.sun@nxp.com>
---
 drivers/tty/serial/fsl_lpuart.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c
index f21915015d67..e9d5b481bb31 100644
--- a/drivers/tty/serial/fsl_lpuart.c
+++ b/drivers/tty/serial/fsl_lpuart.c
@@ -2719,14 +2719,15 @@ static int lpuart_probe(struct platform_device *pdev)
 		lpuart_reg.cons = LPUART_CONSOLE;
 		handler = lpuart_int;
 	}
-	ret = uart_add_one_port(&lpuart_reg, &sport->port);
-	if (ret)
-		goto failed_attach_port;
 
 	ret = lpuart_global_reset(sport);
 	if (ret)
 		goto failed_reset;
 
+	ret = uart_add_one_port(&lpuart_reg, &sport->port);
+	if (ret)
+		goto failed_attach_port;
+
 	ret = uart_get_rs485_mode(&sport->port);
 	if (ret)
 		goto failed_get_rs485;
@@ -2742,9 +2743,9 @@ static int lpuart_probe(struct platform_device *pdev)
 
 failed_irq_request:
 failed_get_rs485:
-failed_reset:
 	uart_remove_one_port(&lpuart_reg, &sport->port);
 failed_attach_port:
+failed_reset:
 	lpuart_disable_clks(sport);
 	return ret;
 }
-- 
2.36.1

Re: [PATCH] serial: fsl_lpuart: Reset prior to registration

[Ilpo Järvinen]

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On Sun, 11 Sep 2022, Lukas Wunner wrote:

> Since commit bd5305dcabbc ("tty: serial: fsl_lpuart: do software reset
> for imx7ulp and imx8qxp"), certain i.MX UARTs are reset after they've
> already been registered.  Register state may thus be clobbered after
> user space has begun to open and access the UART.
> 
> Avoid by performing the reset prior to registration.
> 
> Fixes: bd5305dcabbc ("tty: serial: fsl_lpuart: do software reset for imx7ulp and imx8qxp")
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> Cc: stable@vger.kernel.org # v5.15+
> Cc: Fugang Duan <fugang.duan@nxp.com>
> Cc: Sherry Sun <sherry.sun@nxp.com>

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

-- 
 i.