linux-kernel - Re: [PATCH] lontium-lt9611: check a different register bit for HDMI sensing

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Message-ID: <CALAqxLWn67emfDPcMGrjVag0zCCrNF2=rEiHKQgr2eJ8AotCPg@mail.gmail.com>
Date:   Tue, 16 Nov 2021 20:47:43 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     Peter Collingbourne <pcc@...gle.com>
Cc:     Robert Foss <robert.foss@...aro.org>,
        Vinod Koul <vkoul@...nel.org>,
        Anibal Limon <anibal.limon@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lontium-lt9611: check a different register bit for HDMI sensing

On Tue, Nov 16, 2021 at 6:07 PM Peter Collingbourne <pcc@...gle.com> wrote:
>
> It has been observed that with certain monitors such as the HP Z27n,
> the register 0x825e reads a value of 0x79 when the HDMI cable is
> connected and 0x78 when it is disconnected, i.e. bit 0 appears
> to correspond to the HDMI connection status and bit 2 is never
> set. Therefore, change the driver to check bit 0 instead of bit 2.
>
> Signed-off-by: Peter Collingbourne <pcc@...gle.com>
> Link: https://linux-review.googlesource.com/id/I7e76411127e1ce4988a3f6d0c8ba5f1c3d880c23
> ---
> N.B. I don't currently have easy access to a monitor that works
> with the existing driver, so it would be great if people with
> monitors that currently work could test this patch to make sure
> that it doesn't introduce any regressions. Otherwise I will change
> it to check both bits.

So very interesting! I gave this a spin with my monitors and it works fine.

Vinod: Can you check the datasheet to see if the wrong bit is being used here?

thanks
-john