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Tue, 01 Oct 2019 14:21:22 +0200 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-ap.st.com (STMicroelectronics) with ESMTP id B72B54B; Tue, 1 Oct 2019 12:21:18 +0000 (GMT) Received: from Webmail-eu.st.com (sfhdag5node2.st.com [10.75.127.14]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 1F8D72BEC6E; Tue, 1 Oct 2019 14:21:18 +0200 (CEST) Received: from [10.48.1.171] (10.75.127.49) by SFHDAG5NODE2.st.com (10.75.127.14) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 1 Oct 2019 14:21:17 +0200 Subject: Re: [PATCH] i2c: i2c-stm32f7: fix a race in slave mode with arbitration loss irq To: Fabrice Gasnier , References: <1569919869-3218-1-git-send-email-fabrice.gasnier@st.com> From: Pierre Yves MORDRET Message-ID: Date: Tue, 1 Oct 2019 14:21:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1569919869-3218-1-git-send-email-fabrice.gasnier@st.com> Content-Language: en-US X-Originating-IP: [10.75.127.49] X-ClientProxiedBy: SFHDAG2NODE1.st.com (10.75.127.4) To SFHDAG5NODE2.st.com (10.75.127.14) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,1.0.8 definitions=2019-10-01_06:2019-10-01,2019-10-01 signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191001_052126_108976_64BD9584 X-CRM114-Status: GOOD ( 23.22 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alexandre.torgue@st.com, linux-kernel@vger.kernel.org, alain.volmat@st.com, linux-i2c@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Reviewed-by: Pierre-Yves MORDRET Thx On 10/1/19 10:51 AM, Fabrice Gasnier wrote: > When in slave mode, an arbitration loss (ARLO) may be detected before the > slave had a chance to detect the stop condition (STOPF in ISR). > This is seen when two master + slave adapters switch their roles. It > provokes the i2c bus to be stuck, busy as SCL line is stretched. > - the I2C_SLAVE_STOP event is never generated due to STOPF flag is set but > don't generate an irq (race with ARLO irq, STOPIE is masked). STOPF flag > remains set until next master xfer (e.g. when STOPIE irq get unmasked). > In this case, completion is generated too early: immediately upon new > transfer request (then it doesn't send all data). > - Some data get stuck in TXDR register. As a consequence, the controller > stretches the SCL line: the bus gets busy until a future master transfer > triggers the bus busy / recovery mechanism (this can take time... and > may never happen at all) > > So choice is to let the STOPF being detected by the slave isr handler, > to properly handle this stop condition. E.g. don't mask IRQs in error > handler, when the slave is running. > > Fixes: 60d609f30de2 ("i2c: i2c-stm32f7: Add slave support") > > Signed-off-by: Fabrice Gasnier > --- > drivers/i2c/busses/i2c-stm32f7.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-stm32f7.c b/drivers/i2c/busses/i2c-stm32f7.c > index 266d1c2..3a8ab0c 100644 > --- a/drivers/i2c/busses/i2c-stm32f7.c > +++ b/drivers/i2c/busses/i2c-stm32f7.c > @@ -1501,7 +1501,7 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data) > void __iomem *base = i2c_dev->base; > struct device *dev = i2c_dev->dev; > struct stm32_i2c_dma *dma = i2c_dev->dma; > - u32 mask, status; > + u32 status; > > status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR); > > @@ -1526,12 +1526,15 @@ static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data) > f7_msg->result = -EINVAL; > } > > - /* Disable interrupts */ > - if (stm32f7_i2c_is_slave_registered(i2c_dev)) > - mask = STM32F7_I2C_XFER_IRQ_MASK; > - else > - mask = STM32F7_I2C_ALL_IRQ_MASK; > - stm32f7_i2c_disable_irq(i2c_dev, mask); > + if (!i2c_dev->slave_running) { > + u32 mask; > + /* Disable interrupts */ > + if (stm32f7_i2c_is_slave_registered(i2c_dev)) > + mask = STM32F7_I2C_XFER_IRQ_MASK; > + else > + mask = STM32F7_I2C_ALL_IRQ_MASK; > + stm32f7_i2c_disable_irq(i2c_dev, mask); > + } > > /* Disable dma */ > if (i2c_dev->use_dma) { > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel