Hello Krzysztof, > -----Original Message----- > From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > Sent: Friday, March 3, 2023 4:51 PM > To: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>; Wolfram Sang > <wsa@xxxxxxxxxx> > Cc: Joel Stanley <joel@xxxxxxxxx>; Brendan Higgins > <brendan.higgins@xxxxxxxxx>; Krzysztof Kozlowski > <krzysztof.kozlowski+dt@xxxxxxxxxx>; Andrew Jeffery <andrew@xxxxxxxx>; > devicetree@xxxxxxxxxxxxxxx; Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>; Rob > Herring <robh+dt@xxxxxxxxxx>; Benjamin Herrenschmidt > <benh@xxxxxxxxxxxxxxxxxxx>; linux-aspeed@xxxxxxxxxxxxxxxx; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > openbmc@xxxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx > Subject: Re: [PATCH v6 1/2] dt-bindings: i2c: aspeed: support for AST2600-i2cv2 > > On 03/03/2023 09:28, Ryan Chen wrote: > > Hello Krzysztof, > > > >> -----Original Message----- > >> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > >> Sent: Friday, March 3, 2023 4:20 PM > >> To: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>; Wolfram Sang > >> <wsa@xxxxxxxxxx> > >> Cc: Joel Stanley <joel@xxxxxxxxx>; Brendan Higgins > >> <brendan.higgins@xxxxxxxxx>; Krzysztof Kozlowski > >> <krzysztof.kozlowski+dt@xxxxxxxxxx>; Andrew Jeffery > >> <andrew@xxxxxxxx>; devicetree@xxxxxxxxxxxxxxx; Philipp Zabel > >> <p.zabel@xxxxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Benjamin > >> Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>; > >> linux-aspeed@xxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > >> linux-kernel@xxxxxxxxxxxxxxx; openbmc@xxxxxxxxxxxxxxxx; > >> linux-i2c@xxxxxxxxxxxxxxx > >> Subject: Re: [PATCH v6 1/2] dt-bindings: i2c: aspeed: support for > >> AST2600-i2cv2 > >> > >> On 01/03/2023 06:57, Ryan Chen wrote: > >>> Hello Krzysztof, > >>> > >>>> -----Original Message----- > >>>> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> > >>>> Sent: Monday, February 27, 2023 4:25 PM > >>>> To: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>; Andrew Jeffery > >>>> <andrew@xxxxxxxx>; Brendan Higgins <brendan.higgins@xxxxxxxxx>; > >>>> Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>; Joel Stanley > >>>> <joel@xxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Krzysztof > >>>> Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Philipp Zabel > >>>> <p.zabel@xxxxxxxxxxxxxx>; linux-i2c@xxxxxxxxxxxxxxx; > >>>> openbmc@xxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; > >>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; > >>>> linux-aspeed@xxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > >>>> Subject: Re: [PATCH v6 1/2] dt-bindings: i2c: aspeed: support for > >>>> AST2600-i2cv2 > >>>> > >>>> On 26/02/2023 04:13, Ryan Chen wrote: > >>>>> Add ast2600-i2cv2 compatible and aspeed,global-regs, > >>>>> aspeed,timeout aspeed,xfer-mode description for ast2600-i2cv2. > >>>>> > >>>>> Signed-off-by: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx> > >>>>> --- > >>>>> .../devicetree/bindings/i2c/aspeed,i2c.yaml | 44 > >> +++++++++++++++++++ > >>>>> 1 file changed, 44 insertions(+) > >>>>> > >>>>> diff --git a/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > >>>>> b/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > >>>>> index f597f73ccd87..75de3ce41cf5 100644 > >>>>> --- a/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > >>>>> +++ b/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > >>>>> @@ -49,6 +49,25 @@ properties: > >>>>> description: > >>>>> states that there is another master active on this bus > >>>>> > >>>>> + aspeed,timeout: > >>>>> + type: boolean > >>>>> + description: I2C bus timeout enable for master/slave mode > >>>> > >>>> Nothing improved here in regards to my last comment. > >>> > >>> Yes, as I know your require is about " DT binding to represent > >>> hardware > >> setup" > >>> So I add more description about aspeed,timeout as blow. > >>> > >>> ASPEED SOC chip is server product, i2c bus may have fingerprint > >>> connect to > >> another board. And also support hotplug. > >>> The following is board-specific design example. > >>> Board A Board B > >>> ------------------------- ------------------------ > >>> |i2c bus#1(master/slave) <===fingerprint ===> i2c bus#x (master/slave)| > >>> |i2c bus#2(master)-> tmp i2c device | | > >> | > >>> |i2c bus#3(master)-> adc i2c device | | > >> | > >>> ------------------------- ------------------------ > >>> > >>> aspeed,timout properites: > >>> For example I2C controller as slave mode, and suddenly disconnected. > >>> Slave state machine will keep waiting for master clock in for rx/tx > transmit. > >>> So it need timeout setting to enable timeout unlock controller state. > >>> And in another side. In Master side also need avoid suddenly slave > >> miss(un-plug), Master will timeout and release the SDA/SCL. > >>> > >>> Do you mean add those description into ore aspeed,timout properites > >> description? > >> > >> You are describing here one particular feature you want to enable in > >> the driver which looks non-scalable and more difficult to configure/use. > >> What I was looking for is to describe the actual configuration you have (e.g. > >> multi-master) which leads to enable or disable such feature in your > hardware. > >> Especially that bool value does not scale later to actual timeout > >> values in time (ms)... > >> > >> I don't know I2C that much, but I wonder - why this should be > >> specific to Aspeed I2C and no other I2C controllers implement it? > >> IOW, this looks quite generic and every I2C controller should have > >> it. Adding it specific to Aspeed suggests that either we miss a > >> generic property or this should not be in DT at all (because no one else has > it...). > >> > >> Also I wonder, why you wouldn't enable timeout always... > >> > >> +Cc Wolfram, > >> Maybe you know whether bool "timeout" property for one controller > >> makes sense? Why we do not have it for all controllers? > >> > > Because, i2c bus didn’t specific timeout. > > But SMBus defines a clock low time-out, TIMEOUT of 35 ms. > > > > It have definition in SMBus specification. > > http://smbus.org/specs/SMBus_3_1_20180319.pdf > > You can check Page 18, Note3 that have timeout description. > > Then you have already property for this - "smbus"? To be a property "smbus", that would be a big topic, I saw fsl i2c also have this. https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/i2c/i2c-mpc.yaml#L43-L47 So, I just think the "timeout" property. Best regards, Ryan Chen
