From: Daisuke Yamane <email@example.com> To: Mark Brown <firstname.lastname@example.org> Cc: email@example.com, firstname.lastname@example.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 <email@example.com>: > > 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.
prev parent 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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