linux-kernel - Re: [PATCH v6] ARM: dts: wheat: Fix ADV7513 address usage

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Message-ID: <20180327081652.5v6wqwfjyb2kvimc@verge.net.au>
Date:   Tue, 27 Mar 2018 10:16:52 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Kieran Bingham <kieran.bingham@...asonboard.com>
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6] ARM: dts: wheat: Fix ADV7513 address usage

On Mon, Mar 26, 2018 at 10:04:24AM +0100, Kieran Bingham wrote:
> Hi Simon,
> 
> On 26/03/18 09:31, Simon Horman wrote:
> > On Fri, Mar 23, 2018 at 09:16:13PM +0000, Kieran Bingham wrote:
> >> Hi Simon,
> >>
> >> On 23/03/18 08:51, Simon Horman wrote:
> >>> On Thu, Mar 22, 2018 at 09:30:40PM +0000, Kieran Bingham wrote:
> >>>> The r8a7792 Wheat board has two ADV7513 devices sharing a single I2C
> >>>> bus, however in low power mode the ADV7513 will reset it's slave maps to
> >>>> use the hardware defined default addresses.
> >>>>
> >>>> The ADV7511 driver was adapted to allow the two devices to be registered
> >>>> correctly - but it did not take into account the fault whereby the
> >>>> devices reset the addresses.
> >>>>
> >>>> This results in an address conflict between the device using the default
> >>>> addresses, and the other device if it is in low-power-mode.
> >>>>
> >>>> Repair this issue by moving both devices away from the default address
> >>>> definitions.
> >>>
> >>> Hi Kierean,
> >>>
> >>> as this is a fix
> >>> a) Does it warrant a fixes tag?
> >>>    Fixes: f6eea82a87db ("ARM: dts: wheat: add DU support")
> >>> b) Does it warrant being posted as a fix for v4.16;
> >>> c) or v4.17?
> >>
> >> Tricky one, yes it could but this DTS fix, will only actually 'fix' the issue if
> >> the corresponding driver updates to allow secondary addresses to be parsed are
> >> also backported.
> >>
> >> It should be safe to back port the dts fix without the driver updates, but the
> >> addresses specified by this patch will simply be ignored.
> > 
> > In that case I think its safe to add the fixes tag and take the DTS patch
> > via the renesas tree. Perhaps applying it for v4.18 and allowing automatic
> > backporting to take its course is the cleanest option.
> > 
> >> Thus if this is marked with the fixes tag the corresponding patch "drm: adv7511:
> >> Add support for i2c_new_secondary_device" should also be marked.
> >>
> >> It looks like that patch has yet to be picked up by the DRM subsystem, so how
> >> about I bundle both of these two patches together in a repost along with the
> >> fixes tag.
> >>
> >> In fact, I don't think the ADV7511 dt-bindings update has made any progress
> >> either. (dt-bindings: adv7511: Extend bindings to allow specifying slave map
> >> addresses). The media tree variants for the adv7604 have already been picked up
> >> by Mauro I believe though.
> >>
> >> I presume it would be acceptable for this dts patch (or rather all three patches
> >> mentioned) to get integrated through the DRM tree ?
> > 
> > Unless there is a strong reason I would prefer the dts patch to go via
> > my tree. The reason is to avoid merge conflicts bubbling up to Linus,
> > which really is something best avoided.
> 
> That's perfectly fine with me.
> 
> Feel free to add:
> 
> Fixes: f6eea82a87db ("ARM: dts: wheat: add DU support")
> 
> as you suggested when you apply, or alternatively let me know if you need a repost.

Thanks, applied for v4.18 with the fixes tag.