If the imx driver cannot support RS485 it sets the ports rs485_supported structure to NULL. But it still calls uart_get_rs485_mode() which may set the RS485_ENABLED flag nevertheless.
This may lead to an attempt to configure RS485 even if it is not supported when the flag is evaluated in uart_configure_port() at port startup.
Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED flag is not supported by the caller.
With this fix a check for RTS availability is now obsolete in the imx driver, since it can not evaluate to true any more. Remove this check, too.
Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported") Cc: Shawn Guo shawnguo@kernel.org Cc: Sascha Hauer s.hauer@pengutronix.de Cc: stable@vger.kernel.org Suggested-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com --- drivers/tty/serial/imx.c | 4 ---- drivers/tty/serial/serial_core.c | 3 +++ 2 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 9cffeb23112b..98b78d360a74 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -2328,10 +2328,6 @@ static int imx_uart_probe(struct platform_device *pdev) return ret; }
- if (sport->port.rs485.flags & SER_RS485_ENABLED && - (!sport->have_rtscts && !sport->have_rtsgpio)) - dev_err(&pdev->dev, "no RTS control, disabling rs485\n"); - /* * If using the i.MX UART RTS/CTS control then the RTS (CTS_B) * signal cannot be set low during transmission in case the diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 661074ab8edb..b418952c03df 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -3593,6 +3593,9 @@ int uart_get_rs485_mode(struct uart_port *port) u32 rs485_delay[2]; int ret;
+ if (!(port->rs485_supported.flags & SER_RS485_ENABLED)) + return 0; + ret = device_property_read_u32_array(dev, "rs485-rts-delay", rs485_delay, 2); if (!ret) {
On Sat, 9 Dec 2023, Lino Sanfilippo wrote:
If the imx driver cannot support RS485 it sets the ports rs485_supported structure to NULL.
No, an embedded struct inside struct uart_port cannot be set to NULL, it's always there.
Looking into the code, that setting of rs485_supported from imx_no_rs485 is actually superfluous as it should be already cleared to zeros on alloc.
But it still calls uart_get_rs485_mode() which may set the RS485_ENABLED flag nevertheless.
This may lead to an attempt to configure RS485 even if it is not supported when the flag is evaluated in uart_configure_port() at port startup.
Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED flag is not supported by the caller.
With this fix a check for RTS availability is now obsolete in the imx driver, since it can not evaluate to true any more. Remove this check, too.
Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported") Cc: Shawn Guo shawnguo@kernel.org Cc: Sascha Hauer s.hauer@pengutronix.de Cc: stable@vger.kernel.org Suggested-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com
On 11.12.23 12:00, Ilpo Järvinen wrote:
On Sat, 9 Dec 2023, Lino Sanfilippo wrote:
If the imx driver cannot support RS485 it sets the ports rs485_supported structure to NULL.
No, an embedded struct inside struct uart_port cannot be set to NULL, it's always there.
Hmm, ok. What I meant was that the structure is nullified. "set to NULL" is maybe a bit misleading. I will correct this.
Looking into the code, that setting of rs485_supported from imx_no_rs485 is actually superfluous as it should be already cleared to zeros on alloc.
Yes. BTW: Another "no_rs485" configuration setting can be found in the ar933x driver. If we do not want to keep those assignments I can remove the one for the imx driver with the next version of this patch...
But it still calls uart_get_rs485_mode() which may set the RS485_ENABLED flag nevertheless.
This may lead to an attempt to configure RS485 even if it is not supported when the flag is evaluated in uart_configure_port() at port startup.
Avoid this by bailing out of uart_get_rs485_mode() if the RS485_ENABLED flag is not supported by the caller.
With this fix a check for RTS availability is now obsolete in the imx driver, since it can not evaluate to true any more. Remove this check, too.
Fixes: 00d7a00e2a6f ("serial: imx: Fill in rs485_supported") Cc: Shawn Guo shawnguo@kernel.org Cc: Sascha Hauer s.hauer@pengutronix.de Cc: stable@vger.kernel.org Suggested-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Lino Sanfilippo l.sanfilippo@kunbus.com
On Wed, 13 Dec 2023, Lino Sanfilippo wrote:
On 11.12.23 12:00, Ilpo Järvinen wrote:
On Sat, 9 Dec 2023, Lino Sanfilippo wrote:
Looking into the code, that setting of rs485_supported from imx_no_rs485 is actually superfluous as it should be already cleared to zeros on alloc.
Yes. BTW: Another "no_rs485" configuration setting can be found in the ar933x driver. If we do not want to keep those assignments I can remove the one for the imx driver with the next version of this patch...
I think they can just be dropped as it's normal in Linux code to assume that things are zeroed by default. Those "no"-variants originate from the time when supported_rs485 was not yet embedded but just a pointer to a const struct and I didn't realize I could have removed them when I ended up embedding the struct so it can be altered per port.
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Lino Sanfilippo