linux-kernel - Re: [alsa-devel] regression v4.16 on Nokia N900: sound does not work

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Date:   Fri, 2 Mar 2018 08:22:52 -0600
From:   "Andrew F. Davis" <afd@...com>
To:     Pavel Machek <pavel@....cz>,
        Linus Walleij <linus.walleij@...aro.org>
CC:     Daniel Baluta <daniel.baluta@...il.com>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Linux-ALSA <alsa-devel@...a-project.org>,
        Ivajlo Dimitrov <ivo.g.dimitrov.75@...il.com>,
        Kevin Hilman <khilman@...nel.org>,
        ext Tony Lindgren <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        kernel list <linux-kernel@...r.kernel.org>,
        Sebastian Reichel <sre@...nel.org>,
        Martijn Braam <martijn@...xit.nl>,
        Filip Matijević <filip.matijevic.pz@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mickuláš Qwertz <abcloriens@...il.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Pali Rohár <pali.rohar@...il.com>,
        <clayton@...ftyguy.net>, Linux-OMAP <linux-omap@...r.kernel.org>,
        Patrik Bachan <patrikbachan@...il.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        <serge@...lyn.com>
Subject: Re: [alsa-devel] regression v4.16 on Nokia N900: sound does not work

On 03/02/2018 05:10 AM, Pavel Machek wrote:
> Hi!
> 
>>> If this is taking longer to fix, should c85823390215 be reverted in
>>> the meantime? It does not seem particulary important/urgent...
>>
>> No patience between the v4.16 release candidates eh ;)
>>
>> commit 6662ae6af82df10259a70c7569b4c12ea7f3ba93
>> ("gpiolib: Keep returning EPROBE_DEFER when we should")
>>
>> and
>>
>> commit ce27fb2c56db6ccfe8099343bb4afdab15e77e7b
>> ("gpio: Handle deferred probing in of_find_gpio() properly")
>>
>> that are both in Torvalds' tree since yesterday should be fixing
>> this, I think? Did you try just using the upstream HEAD?
> 
> Ok, so this code looks pretty crazy to me: I tried removing the
> "of_find_spi_gpio" part, and audio started working.
> 
> What is going on with the ()s around == s? You made me look up C
> operator precedence.
> 
> Hmm, and it is also wrong, right? It turns any error code into ENOENT,
> as it tries to do the "special handling".
> 
>                  *                                                                      
>                  * This means we don't need to look any further for                     
>                  * alternate name conventions, and we should really                     
>                  * preserve the return code for our user to be able to                  
>                  * retry probing later.                                                 
>                  */
>                 if (IS_ERR(desc) && PTR_ERR(desc) == -EPROBE_DEFER)
>                         return desc;
> 
>                 if (!IS_ERR(desc) || (PTR_ERR(desc) != -ENOENT))
>                         break;
>         }
> 
>         /* Special handling for SPI GPIOs if used */
>         if (IS_ERR(desc))
>                 desc = of_find_spi_gpio(dev, con_id, &of_flags);
> 
>         /* Special handling for regulator GPIOs if used */
>         if (IS_ERR(desc) && PTR_ERR(desc) != -EPROBE_DEFER)
>                 desc = of_find_regulator_gpio(dev, con_id, &of_flags);
> 
> Something like this?
> 
> diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
> index 84e5a9d..f0fab26 100644
> --- a/drivers/gpio/gpiolib-of.c
> +++ b/drivers/gpio/gpiolib-of.c
> @@ -241,29 +241,17 @@ struct gpio_desc *of_find_gpio(struct device *dev, const char *con_id,
>  
>  		desc = of_get_named_gpiod_flags(dev->of_node, prop_name, idx,
>  						&of_flags);
> -		/*
> -		 * -EPROBE_DEFER in our case means that we found a
> -		 * valid GPIO property, but no controller has been
> -		 * registered so far.
> -		 *
> -		 * This means we don't need to look any further for
> -		 * alternate name conventions, and we should really
> -		 * preserve the return code for our user to be able to
> -		 * retry probing later.
> -		 */
> -		if (IS_ERR(desc) && PTR_ERR(desc) == -EPROBE_DEFER)
> -			return desc;
>  
> -		if (!IS_ERR(desc) || (PTR_ERR(desc) != -ENOENT))
> +		if (!IS_ERR(desc) || PTR_ERR(desc) != -ENOENT)


I rather like the () so one doesn't always have to look up C operator
precedence to verify..


>  			break;
>  	}
>  
>  	/* Special handling for SPI GPIOs if used */
> -	if (IS_ERR(desc))
> +	if (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
>  		desc = of_find_spi_gpio(dev, con_id, &of_flags);
>  
>  	/* Special handling for regulator GPIOs if used */
> -	if (IS_ERR(desc) && PTR_ERR(desc) != -EPROBE_DEFER)
> +	if (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT)
>  		desc = of_find_regulator_gpio(dev, con_id, &of_flags);
>  
>  	if (IS_ERR(desc))
>