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[91.78.208.152]) by smtp.googlemail.com with ESMTPSA id r206sm4596060lff.65.2020.04.24.07.45.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Apr 2020 07:45:50 -0700 (PDT) Subject: Re: [PATCH v2 1/2] i2c: tegra: Better handle case where CPU0 is busy for a long time To: Jon Hunter , Thierry Reding , Laxman Dewangan , Wolfram Sang , Manikanta Maddireddy , Vidya Sagar Cc: linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200324191217.1829-1-digetx@gmail.com> <20200324191217.1829-2-digetx@gmail.com> <1e259e22-c300-663a-e537-18d854e0f478@nvidia.com> <8cd085e1-f9fd-6ec0-9f7a-d5463f176a63@nvidia.com> <6f07e5c8-7916-7ea2-2fe7-d05f8f011471@nvidia.com> <77a31b2f-f525-ba9e-f1ae-2b474465bde4@gmail.com> <470b4de4-e98a-1bdc-049e-6259ad603507@nvidia.com> From: Dmitry Osipenko Message-ID: Date: Fri, 24 Apr 2020 17:45:49 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-i2c-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org 24.04.2020 10:10, Jon Hunter пишет: ... >> Could you please clarify why pm_runtime_get_sync() can't be used by the >> I2C driver's in NOIRQ phase? > > Yes take a look at commit 1e2ef05bb8cf ("PM: Limit race conditions > between runtime PM and system sleep (v2)"). I2C driver now uses irq-safe RPM since ede2299f7 ("i2c: tegra: Support atomic transfers"), and thus, the RPM's workqueue shouldn't be a problem. I guess RPM should work fine in this case, don't you think so? ... >> Yes, keeping PCI regulators always-enabled should be a good immediate >> solution. > > I was thinking about that, and I am not sure it is. I don't think that > the failure to send the I2C command should break suspend. It shouldn't, but looks like it should be a separate problem. .... > So I confirmed that DMA is not the issue in this case. I tested this by > ensuring that DMA is never used. However, it is a potential problem > indeed. > >> Could you please try to apply this hunk and see if it makes any >> difference (I'll probably make it as proper patch): > > Per my tests, I don't believe that it will as disabling DMA does not > resolve the problem. > >> It also could be that there is more than the suspend ordering problem, >> but for now it is hard to tell without having a detailed log which >> includes I2C/DMA/RPM traces. > > I have taken a look and I don't see any issues with ordering. I2C is > suspended after PCI. This did not change. Do you see a "completion done after timeout" messages in the KMSG log of the v5.6 kernel? Could you please try this hunk? Although, I'll be surprised if it changes anything. --- >8 --- diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index 36d7114823ce..7196084b15fd 100644 --- a/drivers/i2c/busses/i2c-tegra.c +++ b/drivers/i2c/busses/i2c-tegra.c @@ -1028,6 +1028,13 @@ tegra_i2c_wait_completion_timeout(struct tegra_i2c_dev *i2c_dev, msecs_to_jiffies(timeout_ms)); disable_irq(i2c_dev->irq); + /* + * There is a chance that completion may happen after IRQ + * synchronization, which is done by disable_irq(). + */ + if (ret == 0 && completion_done(complete)) + ret = 1; + /* * Under some rare circumstances (like running KASAN + * NFS root) CPU, which handles interrupt, may stuck in --- >8 ---