On 15/11/2023 22:53, Chris Packham wrote: > Hi Krystof, > > On 16/11/23 10:29, Krzysztof Kozlowski wrote: >> 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 <chris.packham@xxxxxxxxxxxxxxxxxxx> >>> --- >>> >> ... >> >>> 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. > > That's the kind of breadcrumb I need. Although I can't see > enable-ref-counting as any kind of DT property. Do you mean > GPIOD_FLAGS_BIT_NONEXCLUSIVE? It's not a feature or property of Devicetree, but missing feature of OS. Best regards, Krzysztof
