linux-kernel - Re: [PATCH v2] panel/simple-simple: Identify simple DPI panels using .compatible field

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Message-ID: <aF0Rf8YiriLCN85V@gaggiata.pivistrello.it>
Date: Thu, 26 Jun 2025 11:23:11 +0200
From: Francesco Dolcini <francesco@...cini.it>
To: Anusha Srivatsa <asrivats@...hat.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
	Jessica Zhang <quic_jesszhan@...cinc.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Francesco Dolcini <francesco@...cini.it>
Subject: Re: [PATCH v2] panel/simple-simple: Identify simple DPI panels using
 .compatible field

Hello Anusha,
thanks for your patch

On Wed, Jun 25, 2025 at 05:44:44PM -0500, Anusha Srivatsa wrote:
> The panel allocation in panel_simple_probe() breaks due to not having
> the panel desc for DPI panels. DPI panels gets probed much later.
> 
> Currently driver is checking for desc == &panel_dpi to do the DPI
> specific panel desc allocations. This looks hacky.
> 
> This patch does the following:
> 
> - Rename panel_dpi_probe() to panel_dpi_get_desc() and call it before
> panel allocation. panel_dpi_get_desc() returns a panel desc unlike
> panel_dpi_probe() which returned an int. This way driver has a known
> connector type while allocating the panel.
> - panel_dpi_get_desc() returns a panel desc
> - Add a simple helper is_panel_dpi() to identify a simple DPI panel from
> a simple panel based on .compatible field
> 
> Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
> Suggested-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> Suggested-by: Maxime Ripard <mripard@...nel.org>
> Cc: Francesco Dolcini <francesco@...cini.it>
> Cc: Luca Ceresoli <luca.ceresoli@...tlin.com>
> Cc: Maxime Ripard <mripard@...nel.org>
> Reported-by: Francesco Dolcini <francesco@...cini.it>
> Closes: https://lore.kernel.org/all/20250612081834.GA248237@francesco-nb/
> Signed-off-by: Anusha Srivatsa <asrivats@...hat.com>

Not working for me.

I tested on top of current torvalds/master [1], and the result is display not working, no WARNING
message and this `platform disp0: deferred probe pending: (reason unknown)`.

reverting de04bb0089a9 on top of current master [1] fixes the issue.

[1] commit ee88bddf7f2f ("Merge tag 'bpf-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf")

Francesco