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From: Daisuke Yamane <yamane07ynct@gmail.com>
To: Mark Brown <broonie@kernel.org>
Cc: linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] spi: a3700: fix hang caused by a3700_spi_transfer_one_fifo()
Date: Wed, 1 Jul 2020 22:18:04 +0900
Message-ID: <CAHZ3=rpqq5ZJQUGR54vStbqohcrS_w2beVi4m1S+v=ZWEzVtKg@mail.gmail.com> (raw)
In-Reply-To: <20200630111137.GI5272@sirena.org.uk>

2020年6月30日(火) 20:11 Mark Brown <broonie@kernel.org>:
>
> On Tue, Jun 30, 2020 at 02:44:21AM +0900, Daisuke Yamane wrote:
> > transfer_one() must call spi_finalize_current_transfer() before
> > returning to inform current transfer has finished. Otherwise spi driver
> > doesn't issue next transfer, and hang.
>
> To be clear it can also return a positive value and then finalize later,
> there's no need to finalize before returning (otherwise finalizing would
> be a bit redundant) and if the driver doesn't return a positive value
> there should be no need to finalize at all.
>
> > However a3700_spi_transfer_one_fifo() doesn't call it if waiting for
> > "wfifo empty" or "xfer ready" has timed out.
> > Thus, this patch corrects error handling of them.
>
> The core shouldn't be waiting at all if the driver returned an error, we
> only wait if the return value was positive.  Looking at the code it's
> not clear to me how we manage to end up waiting - it looks like the
> driver passes back the error correctly and the core looks like it does
> the right thing.  Have you seen hangs in operation?
Yes, and I could avoid hanging by this patch. But I also understand that
your point is correct. Probably I'm misunderstanding the cause of the hang.
I will investigate a little more.

      reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29 17:44 Daisuke Yamane
2020-06-30 11:11 ` Mark Brown
2020-07-01 13:18   ` Daisuke Yamane [this message]

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