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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1grfUM-0004n4-DW; Thu, 07 Feb 2019 08:56:54 +0000 Received: from bhuna.collabora.co.uk ([46.235.227.227]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1grfUJ-0004mW-TS for linux-mtd@lists.infradead.org; Thu, 07 Feb 2019 08:56:53 +0000 Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: bbrezillon) by bhuna.collabora.co.uk (Postfix) with ESMTPSA id 1BB2227DFBF; Thu, 7 Feb 2019 08:56:50 +0000 (GMT) Date: Thu, 7 Feb 2019 09:56:47 +0100 From: Boris Brezillon To: "Sobon, Przemyslaw" Subject: Re: [PATCH] cfi: fix deadloop in cfi_cmdset_0002.c do_write_buffer Message-ID: <20190207095635.0fc3b411@kernel.org> In-Reply-To: References: <1548977439-318904-1-git-send-email-liujian56@huawei.com> <20190203092645.18d1495b@bbrezillon> <20190203093509.269bf1e1@bbrezillon> Organization: Collabora X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190207_005652_216337_97506487 X-CRM114-Status: GOOD ( 26.73 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "keescook@chromium.org" , "joakim.tjernlund@infinera.com" , "ikegami@allied-telesis.co.jp" , "richard@nod.at" , "linux-kernel@vger.kernel.org" , "marek.vasut@gmail.com" , "linux-mtd@lists.infradead.org" , "computersforpeace@gmail.com" , "dwmw2@infradead.org" , Liu Jian Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org Hi Sobon, On Tue, 5 Feb 2019 22:28:44 +0000 "Sobon, Przemyslaw" wrote: > > From: Boris Brezillon > > Sent: Sunday, February 3, 2019 12:35 AM > > > +Przemyslaw > > > > > > On Fri, 1 Feb 2019 07:30:39 +0800 > > > Liu Jian wrote: > > > > > > > In function do_write_buffer(), in the for loop, there is a case > > > > chip_ready() returns 1 while chip_good() returns 0, so it never > > > > break the loop. > > > > To fix this, chip_good() is enough and it should timeout if it stay > > > > bad for a while. > > > > > > Looks like Przemyslaw reported and fixed the same problem. > > > > > > > > > > > Fixes: dfeae1073583(mtd: cfi_cmdset_0002: Change write buffer to > > > > check correct value) > > > > > > Can you put the Fixes tag on a single, and the format is > > > > > > Fixes: ("message") > > > > > > > Signed-off-by: Yi Huaijie > > > > Signed-off-by: Liu Jian > > > > > > [1]http://patchwork.ozlabs.org/patch/1025566/ > > > > > > > --- > > > > drivers/mtd/chips/cfi_cmdset_0002.c | 6 +++--- > > > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c > > > > b/drivers/mtd/chips/cfi_cmdset_0002.c > > > > index 72428b6..818e94b 100644 > > > > --- a/drivers/mtd/chips/cfi_cmdset_0002.c > > > > +++ b/drivers/mtd/chips/cfi_cmdset_0002.c > > > > @@ -1876,14 +1876,14 @@ static int __xipram do_write_buffer(struct map_info *map, struct flchip *chip, > > > > continue; > > > > } > > > > > > > > - if (time_after(jiffies, timeo) && !chip_ready(map, adr)) > > > > - break; > > > > - > > > > if (chip_good(map, adr, datum)) { > > > > xip_enable(map, chip, adr); > > > > goto op_done; > > > > } > > > > > > > > + if (time_after(jiffies, timeo)) > > > > + break; > > > > + > > > > /* Latency issues. Drop the lock, wait a while and retry */ > > > > UDELAY(map, chip, adr, 1); > > > > } > > > > > > > BTW, the patch itself looks good to me. Ikegami, can you confirm it does the right thing? > > > > Thanks, > > > > Boris > > > > One comment to this patch. If value is written incorrectly quickly we will be > stuck in the loop even though nothing is going to change. For example a value was > written incorrectly after 1us, the loop was set to 1ms, function will return > after 1ms, this solution is not optimized for performance. I considered same > when working on this change and decided to do it different way. Seems like you're right if we assume that checking for GOOD state does not require a delay after the READY check, but if that's not the case and an extra delay is actually required, you might end up with a BAD status while it could have turned GOOD at some point with the 'check only for GOOD state until we timeout' approach. TBH, I don't know how CFI flashes work, so I'll let you guys sort this out. Regards, Boris ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/