linux-kernel - Re: [PATCH] serial: imx: Avoid probe failure in case of missing gpiolib

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Date:   Thu, 1 Aug 2019 09:28:33 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.de>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        "Pengutronix Kernel Team" <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        "NXP Linux Team" <linux-imx@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Jiri Slaby <jslaby@...e.com>
Subject: Re: [PATCH] serial: imx: Avoid probe failure in case of missing
 gpiolib

Hi Uwe,

On 01.08.19 10:48, Uwe Kleine-König wrote:
> On Thu, Aug 01, 2019 at 08:18:05AM +0000, Schrempf Frieder wrote:
>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>
>> If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() will return
>> -ENOSYS and cause the probing of the imx UART to fail. As the
>> GPIOs are optional, we should continue probing in this case.
> 
> Is this really still the case? On which version did you hit this
> problem?

Yes, I think it is. I used v5.2.5, that already has d99482673f95.

> 
> I would expect that is gone with
> d99482673f950817b30caf3fcdfb31179b050ce1 if not earlier.

I think this is a different problem. If CONFIG_GPIOLIB is disabled, 
mctrl_gpio_init() returns -ENOSYS unconditionally here: [1]. The 
existing patch (d99482673f95) seems to handle the case when 
CONFIG_GPIOLIB is enabled, but no or not all GPIOs are given in the dtb.

The sh-sci.c driver has a similar check to skip this case: [2].

Regards,
Frieder

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/serial_mctrl_gpio.h#n121
[2] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/sh-sci.c#n3290