linux-kernel - Re: [PATCH] spi: set right CS polarity depend on gpiolib

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Date:   Fri, 7 May 2021 16:30:09 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Liguang Zhang <zhangliguang@...ux.alibaba.com>
Cc:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: set right CS polarity depend on gpiolib

On Fri, May 07, 2021 at 10:51:17PM +0800, Liguang Zhang wrote:
> After a kernel upgrade from 4.19 to 5.10, we found that tpm flow control
> always causes TIMEOUT which caused by wrong CS polarity setting depend
> on gpiolib.

>  			if (spi->cs_gpiod)
>  				/* polarity handled by gpiolib */
> -				gpiod_set_value_cansleep(spi->cs_gpiod, activate);
> +				gpiod_set_value_cansleep(spi->cs_gpiod, !enable);

Whatever is going on here it doesn't seem likely that this is a problem
in the SPI core given the widespread use of gpiod based chip selects -
can you provide more explanation of what you're seeing here, how is the
chip select configured, what is the hardware expectation and what
actually ends up happening?

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