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[PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported

Lino Sanfilippo posted 6 patches 2 years, 2 months ago
There is a newer version of this series
[PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported
Posted by Lino Sanfilippo 2 years, 2 months ago 
From: Lino Sanfilippo <l.sanfilippo@kunbus.com>

If the imx driver cannot support RS485 it sets the UARTS rs485_supported
structure to NULL. But it still calls uart_get_rs485_mode() which may set
the RS485_ENABLED flag.
The flag however is evaluated by the serial core in uart_configure_port()
at port startup and thus may lead to an attempt to configure RS485 even if
it is not supported.

Avoid this by calling uart_get_rs485_mode() only if RS485 is actually
supported by the driver. Remove also a check for an error condition
that is not possible any more now.

Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
---
 drivers/tty/serial/imx.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index edb2ec6a5567..87689abc21bd 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2326,16 +2326,14 @@ static int imx_uart_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = uart_get_rs485_mode(&sport->port);
-	if (ret) {
-		clk_disable_unprepare(sport->clk_ipg);
-		return ret;
+	if (sport->port.rs485_supported.flags & SER_RS485_ENABLED) {
+		ret = uart_get_rs485_mode(&sport->port);
+		if (ret) {
+			clk_disable_unprepare(sport->clk_ipg);
+			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
-- 
2.40.1
Re: [PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported
Posted by Uwe Kleine-König 2 years, 2 months ago 
On Fri, Sep 29, 2023 at 12:12:46AM +0200, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> 
> If the imx driver cannot support RS485 it sets the UARTS rs485_supported
> structure to NULL. But it still calls uart_get_rs485_mode() which may set
> the RS485_ENABLED flag.
> The flag however is evaluated by the serial core in uart_configure_port()

I wonder if this is the code location where this problem should be
addressed. Or alternatively don't let uart_get_rs485_mode() set
RS485_ENABLED (and other flags) if rs485_supported doesn't suggest that
this works?

> [...]
> 
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>

I don't know how picky Greg is here, but formally you missed to add an
S-o-b line for the sender of this patch (i.e. you with your gmx
address).

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |
Re: [PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported
Posted by Lino Sanfilippo 2 years, 2 months ago 
Hi,

On 29.09.23 08:39, Uwe Kleine-König wrote:
> On Fri, Sep 29, 2023 at 12:12:46AM +0200, Lino Sanfilippo wrote:
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> If the imx driver cannot support RS485 it sets the UARTS rs485_supported
>> structure to NULL. But it still calls uart_get_rs485_mode() which may set
>> the RS485_ENABLED flag.
>> The flag however is evaluated by the serial core in uart_configure_port()
>
> I wonder if this is the code location where this problem should be
> addressed. Or alternatively don't let uart_get_rs485_mode() set
> RS485_ENABLED (and other flags) if rs485_supported doesn't suggest that
> this works?
>

This is indeed the better solution. Especially since the check is then in the serial
core and all RS485 supporting drivers benefit from it. I will change this for v2, thanks!


>> [...]
>>
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>
> I don't know how picky Greg is here, but formally you missed to add an
> S-o-b line for the sender of this patch (i.e. you with your gmx
> address).
>

Hm, until now there have never been complaints about this. Is this really an issue? Of
course I can also S-o-b with my gmx address but adding two S-o-b's for the same person seems
a bit odd to me...

BR,
Lino

> Best regards
> Uwe
>
Re: [PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported
Posted by Uwe Kleine-König 2 years, 2 months ago 
Hello Lino,

On Fri, Sep 29, 2023 at 03:46:52PM +0200, Lino Sanfilippo wrote:
> On 29.09.23 08:39, Uwe Kleine-König wrote:
> > On Fri, Sep 29, 2023 at 12:12:46AM +0200, Lino Sanfilippo wrote:
> >> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> >
> > I don't know how picky Greg is here, but formally you missed to add an
> > S-o-b line for the sender of this patch (i.e. you with your gmx
> > address).
> >
> 
> Hm, until now there have never been complaints about this. Is this really an issue? Of
> course I can also S-o-b with my gmx address but adding two S-o-b's for the same person seems
> a bit odd to me...

The obvious and easy fix is of course to use the author address to send
the patches. :-)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |
Re: [PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported
Posted by Greg KH 2 years, 2 months ago 
On Fri, Sep 29, 2023 at 12:12:46AM +0200, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> 
> If the imx driver cannot support RS485 it sets the UARTS rs485_supported
> structure to NULL. But it still calls uart_get_rs485_mode() which may set
> the RS485_ENABLED flag.
> The flag however is evaluated by the serial core in uart_configure_port()
> at port startup and thus may lead to an attempt to configure RS485 even if
> it is not supported.
> 
> Avoid this by calling uart_get_rs485_mode() only if RS485 is actually
> supported by the driver. Remove also a check for an error condition
> that is not possible any more now.
> 
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
> ---
>  drivers/tty/serial/imx.c | 14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)

Why is this patch not marked for stable?

thanks,

greg k-h
Re: [PATCH 6/6] serial: imx: do not set RS485 enabled if it is not supported
Posted by Lino Sanfilippo 2 years, 2 months ago 

On 29.09.23 07:51, Greg KH wrote:
> On Fri, Sep 29, 2023 at 12:12:46AM +0200, Lino Sanfilippo wrote:
>> From: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>>
>> If the imx driver cannot support RS485 it sets the UARTS rs485_supported
>> structure to NULL. But it still calls uart_get_rs485_mode() which may set
>> the RS485_ENABLED flag.
>> The flag however is evaluated by the serial core in uart_configure_port()
>> at port startup and thus may lead to an attempt to configure RS485 even if
>> it is not supported.
>>
>> Avoid this by calling uart_get_rs485_mode() only if RS485 is actually
>> supported by the driver. Remove also a check for an error condition
>> that is not possible any more now.
>>
>> Signed-off-by: Lino Sanfilippo <l.sanfilippo@kunbus.com>
>> ---
>>  drivers/tty/serial/imx.c | 14 ++++++--------
>>  1 file changed, 6 insertions(+), 8 deletions(-)
>
> Why is this patch not marked for stable?
>

Right, it should be, I will correct this, thanks!

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