linux-kernel - Re: [PATCH v2 3/5] drm/sysfb: simpledrm: Add support for interconnect paths

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Message-Id: <DB7IA132RX61.200FUO5T7L3I8@fairphone.com>
Date: Wed, 09 Jul 2025 13:59:38 +0200
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Dmitry Baryshkov" <dmitry.baryshkov@....qualcomm.com>
Cc: "Hans de Goede" <hdegoede@...hat.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>, "Rob Herring"
 <robh@...nel.org>, "Krzysztof Kozlowski" <krzk+dt@...nel.org>, "Conor
 Dooley" <conor+dt@...nel.org>, "Javier Martinez Canillas"
 <javierm@...hat.com>, "Helge Deller" <deller@....de>,
 <linux-fbdev@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
 <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/5] drm/sysfb: simpledrm: Add support for
 interconnect paths

Hi Dmitry,

On Sun Jul 6, 2025 at 1:14 PM CEST, Dmitry Baryshkov wrote:
> On Mon, Jun 23, 2025 at 08:44:47AM +0200, Luca Weiss wrote:
>> Some devices might require keeping an interconnect path alive so that
>> the framebuffer continues working. Add support for that by setting the
>> bandwidth requirements appropriately for all provided interconnect
>> paths.
>> 
>> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
>> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
>> ---
>>  drivers/gpu/drm/sysfb/simpledrm.c | 83 +++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 83 insertions(+)
>
> If simpledrm is being replaced by a proper DRM driver (thus removing
> those extra votes), will it prevent ICC device from reaching the sync
> state?

How can I try this out? On Milos I don't have MDSS yet but I can add an
interconnect path on another device to try it.

Are there some prints I can enable, or check sysfs/debugfs to see if it
reached sync state?

I only recall seeing sync_state pending warnings in some instances, but
never that it's synced.

Regards
Luca