On Thu, Mar 18, 2021 at 02:44:48PM +0100, Alain Volmat wrote: > 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://marc.info/?l=linux-i2c&m=159531254413805&w=2 > [2] https://marc.info/?l=linux-renesas-soc&m=159361426409817&w=2 Please use lore.kernel.org links. > > Signed-off-by: Alain Volmat <alain.volmat@xxxxxxxxxxx> > > --- > v2: introduce st,smbus-alert property > --- > Documentation/devicetree/bindings/i2c/st,stm32-i2c.yaml | 5 +++++ > 1 file changed, 5 insertions(+) With that, Reviewed-by: Rob Herring <robh@xxxxxxxxxx> Though I defer to Wolfram whether this could/should be common instead. Rob
