[PATCH v3 10/10] arm64: dts: renesas: gray-hawk-single: Add DisplayPort support

[Geert Uytterhoeven]

On Mon, Dec 16, 2024 at 2:33 PM Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> On Fri, Dec 6, 2024 at 10:33 AM Tomi Valkeinen
> <tomi.valkeinen at ideasonboard.com> wrote:
> > From: Tomi Valkeinen <tomi.valkeinen+renesas at ideasonboard.com>
> >
> > Add support for the mini DP output on the Gray Hawk board.
> >
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas at ideasonboard.com>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> > Tested-by: Geert Uytterhoeven <geert+renesas at glider.be>
>
> Thanks for your patch, which is now commit b1000645dc29701f
> ("arm64: dts: renesas: gray-hawk-single: Add DisplayPort support")
> in renesas-devel/renesas-dts-for-v6.14.
>
> Apparently this patch breaks s2idle on Gray Hawk Single when "[PATCH
> v3 06/10] drm/rcar-du: dsi: Add r8a779h0 support" is not present, or
> when CONFIG_DRM_RCAR_USE_MIPI_DSI is not enabled. If the DSI driver
> is not available, the ti_sn65dsi86.bridge part fails to probe with
> -EPROBE_DEFER and "failed to attach dsi host".  Still, the sn65dsi86
> driver must do something critical, as resuming from s2idle now hangs.
> I haven't identified yet where exactly it hangs.
>
> As a result, s2idle is broken in current renesas-devel, which only
> has the DTS changes.  Perhaps I should drop the DTS until the issue
> is resolved?
>
> However, I suspect White Hawk has the same issue (if
> CONFIG_DRM_RCAR_USE_MIPI_DSI=n), but I cannot verify as my local White
> Hawk is currently not available for kernel testing.

Confirmed on White Hawk by Tomi and me.

When the hang occurs, magic sysrq no longer works. However, the system
still prints "nfs server not responding" once in a while, so I added
calls to various sysrq print functions to rpc_check_timeout().
This revealed that the system is blocked on wait_for_completion()
in dpm_wait_for_superior(), called from device_resume_noirq().
Printing the actual device and parent gives:

    platform fed80000.dsi-encoder: PM: device_resume_noirq
    platform fed80000.dsi-encoder: PM: dpm_wait_for_superior: parent
fed80000.dsi-encoder

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds