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From:   Pintu Agarwal <pintu.ping@gmail.com>
Date:   Wed, 19 Jun 2019 19:03:39 +0530
Message-ID: <CAOuPNLjYhkP_kL+q-ZpiDZMMpOHrU88BFBc2agtnCzXt8dihOg@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 8:39 PM Fabio Estevam <festevam@gmail.com> wrote:
>
> On Tue, Jun 18, 2019 at 11:46 AM Pintu Agarwal <pintu.ping@gmail.com> wrote:
>
> > 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.
>
> Please see this recently submitted patch:
> https://lore.kernel.org/patchwork/patch/1084057/
>
Okay. Thank you for this reference. This can be definitely helpful.
But a quick look may be feel, this is slightly different.
Anyways, I will have a deeper look.

> > 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.
>
> The suggestion I have is to try to use latest mainline kernel. If you
> see any issues with it, please report.
>
> The combination you mentioned in a prior thread (kernel 3.10 +
> backported drm patches 4.9) is not really something the community can
> help you.

You can think that the version I am using right now is almost 4.9 itself.
Upgrading again to higher kernel version is again difficult, also
customer does not want it.
BTW, I am not talking about runtime suspend/resume.
I know it works normally.

I just need some approach and pointers.
Like someone said rightly, I may need to re-implement bind() function
again in resume path.
I already tried doing hdmi_power_on/off and with that I could invoke
hdmi_setup() function, but the system hang after that.

Another approach I tried is, installing hdmi {dw-hdmi.ko,
dw_hdmi-imx.ko} as a module, just after the resume.
With this also system hangs during installation of dw_hdmi-imx.ko at
below location:

imx_drm_driver_load(..)
|
|--> component_bind_all(...)
     |
     |-> component_bind(ipu)
         |
         |
         ipu_drm_bind(..)
         |
         |-> ipu_crtc_init(..)
             |
             |-> ipu_plane_irq(..)
             |
             | ----> << __HANGS HERE__ >>
             |
             |-> devm_request_irq(ipu_irq_handler)

So, ipu_drm_bind() never returns, and hangs.
----------
So, my question is, which approach is better (as a first trial):
1) Installing hdmi as a module, after resume ?
2) Or, implementing the suspend/resume itself ?