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From:   Pintu Agarwal <pintu.ping@gmail.com>
Date:   Tue, 18 Jun 2019 20:15:50 +0530
Message-ID: <CAOuPNLgEEfDca4aeT1+q8GfUfGzbJ4x6JwGf-ROB1pgpXUBHSw@mail.gmail.com>
Subject: Re: [IMX] [DRM]: suspend/resume support
To:     Fabio Estevam <festevam@gmail.com>
Cc:     open list <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>,
        Kernelnewbies <kernelnewbies@kernelnewbies.org>,
        linux-pm@vger.kernel.org
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On Tue, Jun 18, 2019 at 7:32 PM Fabio Estevam <festevam@gmail.com> wrote:
>
> Hi Pintu,
>
> On Mon, Jun 17, 2019 at 10:50 AM Pintu Agarwal <pintu.ping@gmail.com> wrote:
> >
> > Hi All,
> >
> > I am trying to implement suspend/resume functionality to to imx-hdmi driver:
> > https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/gpu/drm/imx/dw_hdmi-imx.c?h=v4.9.181
>
> Please test a recent kernel, such as 5.1.11. I recall that last time
> you reported an issue with the dw hdmi you were running kernel 3.10
> with backported patches from 4.9.
>
> Just tried suspend/resume on a imx6q board and HDMI behaves correctly.

Thank you so much for your reply.
Yes, I already checked the latest mainline kernel changes until 5.2-**.
I see that there are many cleanup related changes, but still I see
that suspend/resume functions are missing in dw_hdmi-imx driver.
So, I am trying to implement myself.
Also, I see that suspend/resume is missing even in :
drivers/gpu/drm/imx/ipuv3-crtc.c
I am trying this also (not sure if we need this as well).

Can you point out some specific patches which can be helpful ?

Currently, what I observed is that hdmi bind() functions are not getting called.
Not sure who is responsible for triggering this bind function.
Or, irq remains disabled after resume, and we need to enable it back
again (but how ?)
Or, we may need to enable vblank events and thus irqs can be enabled.

So, I am exploring many possibilities.
If you have any suggestions please let me know.

Thanks,
Pintu