linux-kernel - Re: Re: [PATCH] spi: atmel: Fix CS and initialization bug

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Message-ID: <cb709000-7816-3817-b734-e03735788723@microchip.com>
Date:   Tue, 29 Jun 2021 17:50:45 +0000
From:   <Dan.Sneddon@...rochip.com>
To:     <broonie@...nel.org>, <Dan.Sneddon@...rochip.com>
CC:     <linux-spi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Tudor.Ambarus@...rochip.com>,
        <Nicolas.Ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <Ludovic.Desroches@...rochip.com>
Subject: Re: Re: [PATCH] spi: atmel: Fix CS and initialization bug

On 6/29/21 10:07 AM, Mark Brown wrote:
> On Tue, Jun 29, 2021 at 05:01:57PM +0000, Dan.Sneddon@...rochip.com wrote:
>> On 6/29/21 9:47 AM, Mark Brown wrote:
> 
>>   >In what way does it do that?  I can't tell what the patch is supposed >to
>>   >do.
> 
>> The SPI_MASTER_GPIO_SS flag has to be set so that the set_cs function
>> gets called even when using gpio cs pins.
> 
> This all needs to be clear in the changelog.

I'll update the commit message.

> 
>>   >> -	enable =3D (!!(spi->mode & SPI_CS_HIGH) =3D=3D enable);
>>   >> =20
>>   >> -	if (enable) {
>>   >> +	if ((enable && (spi->mode & SPI_CS_HIGH))
>>   >> +			|| (!enable && !(spi->mode & SPI_CS_HIGH))) {
> 
>>   >This looks especially suspicious.
> 
>> It's due to the fact that the spi core tells set_cs if the cs should be
>> high or low, not active or disabled.  This logic is to convert from
>> high/low to active/disabled.
> 
> spi_set_cs() handles SPI_CS_HIGH...  this looks like a separate existing
> driver bug, it should just be ignoring SPI_CS_HIGH if it's providing a
> set_cs() operation and letting the core implement SPI_CS_HIGH for it.  I
> only checked breifly but it looks like spi-atmel is trying to use the
> core support for chipselect handling here.
>