Re: [PATCH] dt-bindings: i2c: Add armada-38x i2c binding
From: Rob Herring
Date: Tue Oct 03 2017 - 17:49:33 EST
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.