linux-kernel - [IMX] [DRM]: suspend/resume support

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Message-ID: <CAOuPNLiBA9VjEoG_D2y2O5mKiqsDNW1VZXOk1eWXpGY+h86acg@mail.gmail.com>
Date:   Mon, 17 Jun 2019 19:19:27 +0530
From:   Pintu Agarwal <pintu.ping@...il.com>
To:     open list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Kernelnewbies <kernelnewbies@...nelnewbies.org>,
        linux-pm@...r.kernel.org
Subject: [IMX] [DRM]: suspend/resume support

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

So, I need some help about this.
I logged the request in imx community, but it seems they are not responding.
Firstly I expect nxp community members to support (if anybody here).
Otherwise, I guess, people who are experts here and have prior
experience in implementing suspend/resume for their drivers, should be
able to give me some guidance.

Currently, I am trying to understand what needs to be taken care
during suspend/resume.
With some reference, I figured out that hdmi power off/on needs to be
done during suspend/resume.
But after resume, system is hanging.
It seems like vblank events are not getting triggered after the resume.
May be irq remains disabled after resume, I need to figure out some
way to enable the all the irqs again.

Even if I try to install hdmi driver as a dynamic loadable module,
still I get the same issue.

So, I wonder, what is the right way to handle suspend/resume for any driver.
Some clue/reference should help me to keep going...

Regards,
Pintu