Re: [PATCH] drm: rcar-du: Add r8a77980 support

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Dec 16, 2019 at 11:37:00AM +0100, Geert Uytterhoeven wrote:
> On Mon, Dec 16, 2019 at 10:47 AM Kieran Bingham wrote:
> > On 13/12/2019 00:48, Laurent Pinchart wrote:
> >> On Mon, Dec 09, 2019 at 12:41:07PM +0000, Kieran Bingham wrote:
> >>> On 13/09/2019 10:03, Laurent Pinchart wrote:
> >>>> On Fri, Sep 13, 2019 at 10:21:29AM +0200, Simon Horman wrote:
> >>>>> On Thu, Sep 12, 2019 at 01:00:41PM +0300, Sergei Shtylyov wrote:
> >>>>>> On 11.09.2019 22:25, Kieran Bingham wrote:
> >>>>>>
> >>>>>>> Add direct support for the r8a77980 (V3H).
> >>>>>>>
> >>>>>>> The V3H shares a common, compatible configuration with the r8a77970
> >>>>>>> (V3M) so that device info structure is reused.
> >>>>>>
> >>>>>>    Do we really need to add yet another compatible in this case?
> >>>>>> I just added r8a77970 to the compatible prop in the r8a77980 DT. That's why
> >>>>>> a patch like this one didn't get posted by me.
> >>>>>
> >>>>> The reason for having per-SoC compat strings is that the IP blocks
> >>>>> are not versioned and while we can observe that there are similarities
> >>>>> between, f.e. the DU on the r8a77970 and r8a77980, we can't be certain that
> >>>>> differences may not emerge at some point. By having per-SoC compat strings
> >>>>> we have the flexibility for the driver to address any such differences as
> >>>>> the need arises.
> >>>>>
> >>>>> My recollection is that this scheme has been adopted for non-versioned
> >>>>> Renesas IP blocks since June 2015 and uses of this scheme well before that.
> >>>>
> >>>> Sure, but we could use
> >>>>
> >>>>     compatible = "renesas,du-r8a77980", "renesas,du-r8a77970";
> >
> > We already do in arch/arm64/boot/dts/renesas/r8a77980.dtsi.
> >
> > However that is the *only* non r8a77980 reference in the file so it,
> > itself looks *very* much out of place.
> >
> >
> > Furthermore, the main purpose of this patch is that we clearly document
> > the driver as supporting the r8a77980 in the bindings (No mention that
> > you must use the ..970 binding), yet in actual fact - the driver could
> > not currently support loading a device with the following compatible:
> >
> >         compatible = "renesas,du-r8a77980";
> >
> >
> >>>> in DT without updating the driver. If the r8a77980 turns out to be
> >>>> different, we'll then update the driver without a need to modify DT. I'm
> >>>> fine either way, so
> >>>>
> >>>> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >>>
> >>> Thanks,
> >>>
> >>> This patch has an RB tag from you, and Simon, but alas I don't believe
> >>> it has been picked up in your drm/du/next branch.
> >>>
> >>> Is this patch acceptable? Or do I need to repost?
> >>
> >> Could you just confirm I should apply this patch, and not go for the
> >> alternative proposal above ?
> >
> > I believe the alternative proposal above is what we have today isn't it?
> >
> >
> > Yes, I do believe we should apply this patch.
> 
> +1.
> 
> I'm waiting for the driver part to go upstream, so I can apply the DTS patch.
> Note that this will lead to a messy situation in LTS, as the DTS patch will
> likely be backported, so the driver part must be backported, too.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

and taken in my tree.

> > I'm going to assume you haven't read the other arguments on this thread
> > so I'll paste them here:
> 
> Thanks for recollecting! ;-)

-- 
Regards,

Laurent Pinchart