Hi Gregory, On 27/09/17 00:56, Gregory CLEMENT wrote: > Hi Kalyan, > > Please try avoid top-posting. > > On dim., sept. 24 2017, Kalyan Kinthada <Kalyan.Kinthada@xxxxxxxxxxxxxxxxxxx> wrote: > >> Hi Gregory, >> >> I got this information from Armada-38x functional errata document. > > OK but in any case just adding a new compatible was not enough you have > to update the driver in the same time, however for this case we won't > need it, see below. > >> >> I can add the "marvell,mv78230-i2c" compatible string to the appropriate device tree files >> but the i2c-mv64xxx driver enables an additional feature (offload i2c transactions) >> based on the compatible string "marvell,mv78230-i2c". >> >> I am not sure if this feature (offload i2c transactions) should be enabled for Armada-38x devices. >> That is the reason I felt for the need of a new compatible string >> specifically for Armada-38x SoCs. > > Indeed the Armada-38x SoCs does not support hardware offloading (at > least according the datasheet). But it happens that in the earlier > version of the Armada XP the hardware offloading was buggy, so we > introduced a compatible for this case: marvell,mv78230-a0-i2c. This > compatible enable the errata fix but not the offloading feature. That > means that it is exactly the compatible you need for Armada 38x (and > Armada 39x and 375 I think). The "mv78230-a0-i2c" dt-binding has the following note Note: Only use "marvell,mv78230-a0-i2c" for a very rare, initial version of the SoC which had broken offload support. Linux auto-detects this and sets it appropriately. If we are going to re-use this binding for armada-38x we should probably remove this note. Personally my preference would be an armada-38x compatible string (or 370 if that's the common base of these SoCs). But of course we'll go with whatever your preference is as maintainer. > > Gregory > >> >> Thanks, >> Kalyan >> ________________________________________ >> From: Gregory CLEMENT <gregory.clement@xxxxxxxxxxxxxxxxxx> >> Sent: Friday, 22 September 2017 7:30 p.m. >> To: Kalyan Kinthada >> Cc: devicetree@xxxxxxxxxxxxxxx; wsa@xxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; >> pawel.moll@xxxxxxx; mark.rutland@xxxxxxx; >> ijc+devicetree@xxxxxxxxxxxxxx; galak@xxxxxxxxxxxxxx; >> linux-i2c@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Chris Packham >> Subject: Re: [PATCH] dt-bindings: i2c: Add armada-38x i2c binding >> >> Hi Kalyan, >> >> On ven., sept. 22 2017, Kalyan Kinthada <kalyan.kinthada@xxxxxxxxxxxxxxxxxxx> wrote: >> >>> All armada-38x variants(380, 385, 388) SoCs have an issue >>> in i2c controller which violates the i2c repeated start timing. >> >> >> Did you had an issue with one of the SoC ? >> If yes what was your setting ? >> On my side I never managed to have this sort of issue on Armada 38x. >> >>> >>> This errata is fixed in the i2c-mv64xxx driver but enabled >>> only for devices with compatible string "marvell,mv78230-i2c". >> >> In this case why not just adding the "marvell,mv78230-i2c" as compatible >> string in the appropriate device tree files ? >> >> Gregory >> >>> >>> This patch introduces a new compatible string >>> "marvell,armada-38x-i2c" for the i2c controller on armada-38x SoCs >>> so that the workaound is enabled. >> >> >>> >>> Signed-off-by: Kalyan Kinthada <kalyan.kinthada@xxxxxxxxxxxxxxxxxxx> >>> --- >>> Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt | 1 + >>> 1 file changed, 1 insertion(+) >>> >>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt b/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt >>> index 5c30026921..fc100b6bdb 100644 >>> --- a/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt >>> +++ b/Documentation/devicetree/bindings/i2c/i2c-mv64xxx.txt >>> @@ -14,6 +14,7 @@ Required properties : >>> very rare, initial version of the SoC which >>> had broken offload support. Linux >>> auto-detects this and sets it appropriately. >>> + - "marvell,armada-38x-i2c" >>> - interrupts : The interrupt number >>> >>> Optional properties : >>> -- >>> 2.14.1 >>> >> >> -- >> Gregory Clement, Free Electrons >> Kernel, drivers, real-time and embedded Linux >> development, consulting, training and support. >> http://free-electrons.com > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
