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: <9400d900-f315-815f-a358-16ed4963da6c@csgroup.eu>
Date:   Thu, 14 Jan 2021 12:27:42 +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 13/01/2021 à 13:33, Mark Brown a écrit :
> On Wed, Jan 13, 2021 at 09:49:12AM +0100, Christophe Leroy wrote:
> 
>> With commit 766c6b63aa04 ("spi: fix client driver breakages when using GPIO
>> descriptors") reverted, it is back to work:
> 
> ...
> 
>> What shall I do ?
> 
> I would guess that there's an error with the chip select polarity
> configuration on your system that just happened to work previously, I'd
> suggest fixing this in the board configuration to bring it in line with
> everything else.
> 

Not that easy.

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.

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.

Whereas reverting the above mentionned commit sets back SPI_CS_HIGH into spi->mode without changing 
the ACTIVE level of the GPIO, resulting in the correct polarity.

So, I'm a bit lost, where is the problem exactly ?

Thanks
Christophe