linux-kernel - Re: [PATCH 1/6] serial: Do not hold the port lock when setting rx-during-tx GPIO

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Message-ID: <2023092906-untainted-entangled-4d17@gregkh>
Date:   Fri, 29 Sep 2023 07:50:32 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     jirislaby@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
        ilpo.jarvinen@...ux.intel.com, mcoquelin.stm32@...il.com,
        alexandre.torgue@...s.st.com, linux-kernel@...r.kernel.org,
        linux-serial@...r.kernel.org, l.sanfilippo@...bus.com,
        lukas@...ner.de, p.rosenberger@...bus.com, stable@...r.kernel.org
Subject: Re: [PATCH 1/6] serial: Do not hold the port lock when setting
 rx-during-tx GPIO

On Fri, Sep 29, 2023 at 12:12:41AM +0200, Lino Sanfilippo wrote:
> From: Lino Sanfilippo <l.sanfilippo@...bus.com>
> 
> Both the imx and stm32 driver set the rx-during-tx GPIO in the
> rs485_config() function by means of gpiod_set_value(). Since rs485_config()
> is called with the port lock held, this can be an problem in case that
> setting the GPIO line can sleep (e.g. if a GPIO expander is used which is
> connected via SPI or I2C).
> 
> Avoid this issue by setting the GPIO outside of the port lock in the serial
> core and by using gpiod_set_value_cansleep() instead of gpiod_set_value().
> 
> Since now both the term and the rx-during-tx GPIO are set within the serial
> core use a common function uart_set_rs485_gpios() to set both.
> 
> With moving it into the serial core setting the rx-during-tx GPIO is now
> automatically done for all drivers that support such a GPIO.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Lino Sanfilippo <l.sanfilippo@...bus.com>

You cc: stable on many of these, but do not provide a "Fixes:" tag
showing just how far back they should go.  Can you do that so that we
have a hint as to what to do here?

thanks,

greg k-h