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"? Best regards, Krzysztof
