linux-kernel - Re: [PATCH] spi: Fix incorrect cs

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Message-ID: <3c94fa29-6c21-9fbd-b1f5-eb6c846054bb@marcan.st>
Date:   Sat, 11 Dec 2021 01:32:06 +0900
From:   Hector Martin <marcan@...can.st>
To:     Mark Brown <broonie@...nel.org>
Cc:     Alexandru Ardelean <alexandru.ardelean@...log.com>,
        linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Joey Gouly <joey.gouly@....com>
Subject: Re: [PATCH] spi: Fix incorrect cs_setup delay handling

On 11/12/2021 01.21, Mark Brown wrote:
> On Sat, Dec 11, 2021 at 12:36:34AM +0900, Hector Martin wrote:
> 
>> We need to wait *after* asserting CS and before the transfer, not before
>> asserting CS which isn't very useful.
> 
> This needs a better changelog, there's multiple delays being handled
> here and it's not clear from this which are affected here or what the
> problem is.

cs_setup is affected, I thought at least that was clear from the patch 
summary :-)

 From spi.h:

* @cs_setup: delay to be introduced by the controller after CS is asserted

So clearly that delay has to happen at the end of spi_set_cs, *after* 
the assertion, not at the beginning before it.

If you prefer, I can resend it with a reference to the spi.h comment.

-- 
Hector Martin (marcan@...can.st)
Public Key: https://mrcn.st/pub