Hi Rob, On mer., oct. 04 2017, Rob Herring <robh@xxxxxxxxxx> wrote: > On Wed, Oct 4, 2017 at 3:33 AM, Gregory CLEMENT > <gregory.clement@xxxxxxxxxxxxxxxxxx> wrote: >> Hi Rob, >> >> On mar., oct. 03 2017, Rob Herring <robh@xxxxxxxxxx> wrote: >> >>> On Wed, Sep 27, 2017 at 09:33:00AM +0200, Gregory CLEMENT wrote: >>>> Hi Chris, >>>> >>>> On mer., sept. 27 2017, Chris Packham <Chris.Packham@xxxxxxxxxxxxxxxxxxx> wrote: >>>> >>>> > 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 >>>> >>>> Updating the documentation is the right thing to do yes. >>>> >>>> >>>> > 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. >>>> >>>> If the IP is compatible then there is no reason to add a new one, else >>>> we will end with a compatible for each SoC and the compatible property >>>> will just loose its meaning. >>> >>> If you all had added compatibles for each SoC in the first place, then >>> we wouldn't be having this dicussion. >> >> Really?? >> >> For Armada 38x we have already 6 flavor 381, 382, 383, 385, 388. Then >> we have 9 SoC families on mvebu: orion5x, kirkwood, dove, Armada 370, >> Armada XP, Armada 375, Armada 39x, Armada 7K, Armada 8K. Of course in >> each family we have several flavors. >> >> But then Allwiner also use this driver in 8 SoC families: sun4i, sun5i, >> sun6i, sun7i, sun8i, sun9i, sunxi, sun50i. Here again each family have >> their own flavor. >> >> So you are just suggesting to blot the i2c driver with more than 50 >> compatible string! > > No. > >> That also mean updating the i2c driver each time a new SoC flavor >> appear, so more or less for each release. > > No. You can have one or several fallbacks. Use the fallback as long as > you think they are the same and then add the more specific one to the > driver when you find differences. So you mean adding all the possible variant of the SoC in the binding documentation, but only implement them in the driver when needed? Gregory > > Rob -- Gregory Clement, Free Electrons Kernel, drivers, real-time and embedded Linux development, consulting, training and support. http://free-electrons.com
