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Wed, 18 Feb 2026 08:37:56 -0800 (PST) Received: from eichest-laptop ([178.197.206.239]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43796ac8d46sm43928122f8f.32.2026.02.18.08.37.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 18 Feb 2026 08:37:56 -0800 (PST) Date: Wed, 18 Feb 2026 17:37:54 +0100 From: Stefan Eichenberger To: Frank Li Cc: o.rempel@pengutronix.de, kernel@pengutronix.de, andi.shyti@kernel.org, s.hauer@pengutronix.de, festevam@gmail.com, stefan.eichenberger@toradex.com, francesco.dolcini@toradex.com, linux-i2c@vger.kernel.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v1 2/2] i2c: imx: ensure no clock is generated after last read Message-ID: References: <20260218150940.131354-1-eichest@gmail.com> <20260218150940.131354-3-eichest@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260218_083759_280990_94F5E15F X-CRM114-Status: GOOD ( 14.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Frank, On Wed, Feb 18, 2026 at 11:26:52AM -0500, Frank Li wrote: > On Wed, Feb 18, 2026 at 04:08:50PM +0100, Stefan Eichenberger wrote: > > From: Stefan Eichenberger > > > > When reading from the I2DR register, right after releasing the bus by > > clearing MSTA and MTX, the I2C controller might still generate an > > additional clock cycle which can cause devices to misbehave. Ensure to > > Do you means SCL have additional toggle? You capture waveform? > Yes exactly. We were able to capture the waveform when the issue happens. It doesn't always happen though, it depends on how much time passes between clearing MSTA and MTX and reading from I2DR. If you want to see the waveform, I uploaded it to our server: https://share.toradex.com/dwnhcrl6b9toib6 You can see the additional clock at the right end, after "0x17 + NAK". Regards, Stefan