From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Grygorii.Strashko-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" Subject: Re: [PATCH v3 4/5] i2c: davinci: use bus recovery infrastructure Date: Mon, 06 Apr 2015 16:11:47 +0300 Message-ID: <55228613.2060607@linaro.org> References: <1417448047-15236-1-git-send-email-grygorii.strashko@ti.com> <1417448047-15236-5-git-send-email-grygorii.strashko@ti.com> <20150318203151.GA12072@katana> <550C67D6.3080909@linaro.org> <20150403201846.GH2016@katana> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150403201846.GH2016@katana> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Wolfram Sang , "Grygorii.Strashko-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org" Cc: Kevin Hilman , Santosh Shilimkar , Sekhar Nori , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Murali Karicheri , Alexander Sverdlin , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, =?windows-1252?Q?Uwe_Kleine-K=F6nig?= , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-i2c@vger.kernel.org On 04/03/2015 11:18 PM, Wolfram Sang wrote: > >>> The I2C specs say in 3.1.16 that the recovery procedure should be used >>> when SDA is stuck low. So, I do wonder if we should apply the recovery >>> after a timeout. Stuck SDA might be one reason for timeout, but there >>> may be others... >> >> This is ancient code. And regarding your question - >> Might be it would be reasonable to add call of >> i2c_davinci_wait_bus_not_busy() at the end of i2c_davinci_xfer()? >> This way we will wait for Bus Free before performing recovery. > > That might be an improvement, but the generic question still remains: > Is a timeout a reason for recovery? SDA stuck low is one reason for a > timeout. I have problems making up my mind here between being pragmatic > and being in accordance with the specs. The timeout here means there were no responses from I2C controller within some reasonable time period (default - 1 sec). Which in turn means that Bus/HW state is "unknown" and init&recovery seems reasonable here, but yes - "init&recovery" could be optimized more, but, in my opinion, only as subsequent patches. Actually, i2c_generic_recovery() will just exit if SDA is high already. > >> Of course, i2c_davinci_wait_bus_not_busy() has to be fixed first >> as proposed by Alexander Sverdlin here: >> https://patchwork.ozlabs.org/patch/448994/. > > Okay, good that you said it. So I'll give his patch series priority over > this one. Sorry, but this series already mises few merge windows and it has a lot of revied-by and tested-by, so could we proceed please? Re-based & re-sent http://www.spinics.net/lists/arm-kernel/msg410810.html -- regards, -grygorii