linux-kernel - Re: [PATCH v6] drm/bridge: ti-sn65dsi86: Add HPD for DisplayPort connector type

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Message-ID: <CAD=FV=WgLCwZ5De1B0Cs6MS7310xRa45po_LW7065W2bPNT3Xg@mail.gmail.com>
Date: Tue, 24 Jun 2025 13:59:04 -0700
From: Doug Anderson <dianders@...omium.org>
To: Jayesh Choudhary <j-choudhary@...com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, dri-devel@...ts.freedesktop.org, 
	devarsht@...com, tomi.valkeinen@...asonboard.com, 
	kieran.bingham+renesas@...asonboard.com, ernest.vanhoecke@...adex.com, 
	jonas@...boo.se, jernej.skrabec@...il.com, maarten.lankhorst@...ux.intel.com, 
	mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch, 
	linux-kernel@...r.kernel.org, max.oss.09@...il.com, geert@...ux-m68k.org
Subject: Re: [PATCH v6] drm/bridge: ti-sn65dsi86: Add HPD for DisplayPort
 connector type

Hi,

On Mon, Jun 23, 2025 at 9:48 PM Jayesh Choudhary <j-choudhary@...com> wrote:
>
> By default, HPD was disabled on SN65DSI86 bridge. When the driver was
> added (commit "a095f15c00e27"), the HPD_DISABLE bit was set in pre-enable
> call which was moved to other function calls subsequently.
> Later on, commit "c312b0df3b13" added detect utility for DP mode. But with
> HPD_DISABLE bit set, all the HPD events are disabled[0] and the debounced
> state always return 1 (always connected state).
>
> Set HPD_DISABLE bit conditionally based on display sink's connector type.
> Since the HPD_STATE is reflected correctly only after waiting for debounce
> time (~100-400ms) and adding this delay in detect() is not feasible
> owing to the performace impact (glitches and frame drop), remove runtime
> calls in detect() and add hpd_enable()/disable() bridge hooks with runtime
> calls, to detect hpd properly without any delay.
>
> [0]: <https://www.ti.com/lit/gpn/SN65DSI86> (Pg. 32)
>
> Fixes: c312b0df3b13 ("drm/bridge: ti-sn65dsi86: Implement bridge connector operations for DP")
> Cc: Max Krummenacher <max.krummenacher@...adex.com>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
> Tested-by: Ernest Van Hoecke <ernest.vanhoecke@...adex.com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> ---
>
> Changelog v5->v6:
> - Drop pm_runtime_mark_last_busy()
> - Pick up tags
>
> v5 patch link:
> <https://lore.kernel.org/all/20250616093240.499094-1-j-choudhary@ti.com/>
>
> Changelog v4->v5:
> - Make suspend asynchronous in hpd_disable()
> - Update HPD_DISABLE in probe function to address the case for when
>   comms are already enabled. Comments taken verbatim from [2]
> - Update comments
>
> v4 patch link:
> <https://lore.kernel.org/all/20250611052947.5776-1-j-choudhary@ti.com/>
>
> Changelog v3->v4:
> - Remove "no-hpd" support due to backward compatibility issues
> - Change the conditional from "no-hpd" back to connector type
>   but still address [1]
>
> v3 patch link:
> <https://lore.kernel.org/all/20250529110418.481756-1-j-choudhary@ti.com/>
>
> Changelog v2->v3:
> - Change conditional based on no-hpd property to address [1]
> - Remove runtime calls in detect() with appropriate comments
> - Add hpd_enable() and hpd_disable() in drm_bridge_funcs
>
> v2 patch link:
> <https://lore.kernel.org/all/20250508115433.449102-1-j-choudhary@ti.com/>
>
> Changelog v1->v2:
> - Drop additional property in bindings and use conditional.
> - Instead of register read for HPD state, use dpcd read which returns 0
>   for success and error codes for no connection
> - Add relevant history for the required change in commit message
> - Drop RFC subject-prefix in v2
> - Add "Cc:" tag
>
> v1 patch link:
> <https://lore.kernel.org/all/20250424105432.255309-1-j-choudhary@ti.com/>
>
> [1]: <https://lore.kernel.org/all/mwh35anw57d6nvre3sguetzq3miu4kd43rokegvul7fk266lys@5h2euthpk7vq/>
> [2]: <https://lore.kernel.org/all/CAD=FV=WvH73d78De3PrbiG7b6OaS_BysGtxQ=mJTj4z-h0LYWA@mail.gmail.com/>
>
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 69 +++++++++++++++++++++++----
>  1 file changed, 60 insertions(+), 9 deletions(-)

I'll plan to push this to drm-misc-fixes tomorrow morning unless there
are any objections or requests for me to wait.

-Doug