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Wed, 15 Nov 2023 13:29:56 -0800 (PST) Received: from [172.25.83.73] ([12.186.190.2]) by smtp.gmail.com with ESMTPSA id g9-20020ac84dc9000000b0041cb787ff41sm3793918qtw.67.2023.11.15.13.29.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Nov 2023 13:29:56 -0800 (PST) Message-ID: Date: Wed, 15 Nov 2023 22:29:55 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/2] dt-bindings: i2c: add bus-reset-gpios property Content-Language: en-US To: Chris Packham , wsa@kernel.org, andi.shyti@kernel.org, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, gregory.clement@bootlin.com Cc: linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20231115035753.925534-1-chris.packham@alliedtelesis.co.nz> <20231115035753.925534-2-chris.packham@alliedtelesis.co.nz> From: Krzysztof Kozlowski Autocrypt: addr=krzysztof.kozlowski@linaro.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 15/11/2023 04:57, Chris Packham wrote: > Add bus-reset-gpios and bus-reset-duration-us properties to the binding > description for i2c busses. These can be used to describe hardware where > a common reset GPIO is connected to all downstream devices on and I2C > bus. This reset will be asserted then released before the downstream > devices on the bus are probed. > > Signed-off-by: Chris Packham > --- > ... > > Documentation/devicetree/bindings/i2c/i2c.txt | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/Documentation/devicetree/bindings/i2c/i2c.txt b/Documentation/devicetree/bindings/i2c/i2c.txt > index fc3dd7ec0445..3f95d71b9985 100644 > --- a/Documentation/devicetree/bindings/i2c/i2c.txt > +++ b/Documentation/devicetree/bindings/i2c/i2c.txt > @@ -99,6 +99,14 @@ wants to support one of the below features, it should adapt these bindings. > indicates that the system is accessible via this bus as an endpoint for > MCTP over I2C transport. > > +- bus-reset-gpios: > + GPIO pin providing a common reset for all downstream devices. This GPIO > + will be asserted then released before the downstream devices are probed. I initially reviewed it, but did not think enough about it. After more consideration, I believe this is not a property of the I2C bus controller. This is a property of each device, even if the GPIO is the same. Linux kernel already supports shared GPIO, so you only need enable-ref-counting on it. Putting it into the controller bindings looks like solving OS issue with incorrect hardware description. Best regards, Krzysztof