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Mon, 29 Mar 2021 08:09:10 +0200 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id 322AF10003B; Mon, 29 Mar 2021 08:09:09 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag2node3.st.com [10.75.127.6]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 22F14221773; Mon, 29 Mar 2021 08:09:09 +0200 (CEST) Received: from localhost (10.75.127.47) by SFHDAG2NODE3.st.com (10.75.127.6) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 29 Mar 2021 08:09:08 +0200 From: Alain Volmat To: , CC: , , , , , , , , , , Subject: [PATCH v3 1/2] dt-bindings: i2c: stm32f7: add st, smbus-alert binding for SMBus Alert Date: Mon, 29 Mar 2021 08:09:04 +0200 Message-ID: <1616998145-28278-2-git-send-email-alain.volmat@foss.st.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1616998145-28278-1-git-send-email-alain.volmat@foss.st.com> References: <1616998145-28278-1-git-send-email-alain.volmat@foss.st.com> MIME-Version: 1.0 X-Originating-IP: [10.75.127.47] X-ClientProxiedBy: SFHDAG1NODE1.st.com (10.75.127.1) To SFHDAG2NODE3.st.com (10.75.127.6) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.761 definitions=2021-03-29_02:2021-03-26, 2021-03-29 signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210329_070936_150770_3F1D0F5F X-CRM114-Status: GOOD ( 15.32 ) 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 Based on the SMBus specification, SMBus Alert active state is low. As often on SoC, the SMBus Alert pin is not only dedicated to this feature and can also be used for another purpose (by configuring it as alternate function for other functions via pinctrl). "smbus" dt-binding has been introduced recently [1], however it is also used to indicate usage of host-notify feature. Relying on 'smbus' binding for SMBus-Alert as well as it was discussed previously [2] would lead to requiring the SMBALERT# pin to be configured as alternate function for i2c/smbus controller even if only host-notify is needed. Indeed, not doing so would lead to spurious SMBus Alert interrupts since the i2c/smbus controller would see the (not configured) SMBA pin as low level. For that reason, SMBus-Alert needs to have its own binding in order to only be enabled whenever SMBALERT# pin is configured as alternate function for i2c/smbus controller. [1] https://lore.kernel.org/linux-i2c/20200721062217.GA1044@kunai/ [2] https://lore.kernel.org/linux-i2c/20200701143738.GF3457@gnbcxd0016.gnb.st.com/ Signed-off-by: Alain Volmat Reviewed-by: Rob Herring --- v3: use lore.kernel.org links v2: introduce st,smbus-alert property --- Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml b/Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml index d747f4990ad8..0d45ead7d835 100644 --- a/Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml +++ b/Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml @@ -36,6 +36,11 @@ allOf: minItems: 3 maxItems: 3 + st,smbus-alert: + description: Enable the SMBus-Alert via SMBA pin, note SMBA pin + must also be configured via pinctrl. + type: boolean + - if: properties: compatible: