linux-kernel - Re: SPI not working on 5.10 and 5.11, bisected to 766c6b63aa04 ("spi: fix client driver breakages when using GPIO descriptors")

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Message-ID: <006d1594-8eec-3aad-1651-919071e89f3b@csgroup.eu>
Date:   Thu, 14 Jan 2021 13:33:50 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Mark Brown <broonie@...nel.org>
Cc:     Sven Van Asbroeck <thesven73@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxppc-dev@...abs.org" <linuxppc-dev@...abs.org>
Subject: Re: SPI not working on 5.10 and 5.11, bisected to 766c6b63aa04 ("spi:
 fix client driver breakages when using GPIO descriptors")



Le 14/01/2021 à 12:59, Mark Brown a écrit :
> On Thu, Jan 14, 2021 at 12:27:42PM +0100, Christophe Leroy wrote:
> 
>> Today I have in the DTS the CS GPIOs declared as ACTIVE_LOW.
> 
>> If I declare them as ACTIVE_HIGH instead, then I also have to set
>> spi-cs-high property, otherwise of_gpio_flags_quirks() is not happy and
>> forces the GPIO ACTIVE LOW.
> 
>> When I set spi-cs-high property, it sets the SPI_CS_HIGH bit in spi->mode.
> 
> OK, so it sounds like you want SPI_CS_HIGH and that is being set
> correctly?
> 
>> In fsl_spi_chipselect(), we have
>>
>> 	bool pol = spi->mode & SPI_CS_HIGH
>>
>> Then
>> 	pdata->cs_control(spi, pol);
> 
>> So changing the board config is compensated by the above, and at the end it still doesn't work.
> 
> This is a driver bug, the driver set_cs() operation should not be
> modifying the value it is told to set.
> 

A driver bug ? Or maybe a change forgotten in commit  766c6b63aa04 ("spi: fix client driver 
breakages when using GPIO descriptors") ?

I'm almost sure it was not a bug, it is in line which what is said in the comment removed by the 
above mentionned commit.

I'll send a fix.

Christophe