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

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Message-ID: <20180326083143.r6jz6csckd4ljnpu@verge.net.au>
Date:   Mon, 26 Mar 2018 10:31:43 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     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 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.