linux-kernel - Re: [PATCH v2] drm/simpledrm: Add support for multiple "power-domains"

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Date:   Tue, 19 Sep 2023 15:50:00 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Sven Peter <sven@...npeter.dev>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Janne Grunau <j@...nau.net>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev
Subject: Re: [PATCH v2] drm/simpledrm: Add support for multiple "power-domains"

"Sven Peter" <sven@...npeter.dev> writes:

> Hi,
>
>
> On Mon, Sep 18, 2023, at 09:11, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 12.09.23 um 22:22 schrieb Janne Grunau via B4 Relay:
>>> From: Janne Grunau <j@...nau.net>
>>> 
>>> Multiple power domains need to be handled explicitly in each driver. The
>>> driver core can not handle it automatically since it is not aware of
>>> power sequencing requirements the hardware might have. This is not a
>>> problem for simpledrm since everything is expected to be powered on by
>>> the bootloader. simpledrm has just ensure it remains powered on during
>>> its lifetime.
>>> This is required on Apple silicon M2 and M2 Pro/Max/Ultra desktop
>>> systems. The HDMI output initialized by the bootloader requires keeping
>>> the display controller and a DP phy power domain on.
>>> 
>>> Signed-off-by: Janne Grunau <j@...nau.net>
>>
>> As a simpledrm patch:
>>
>> Reviewed-by: Thomas Zimmermann <tzimmermann@...e.de>
>>
>> Do you want to wait for another review from  someone with 
>> power-management expertise?
>
> I can't claim to have a lot of genpd experience but we use very similar
> code in a few other M1/M2 drivers that also require multiple power domains
> to be up without any sequencing constraints. So for whatever it's worth:
>
> Reviewed-by: Sven Peter <sven@...npeter.dev>
>

Can't claim to be an expert on genpd either but it looks good to me as well.

Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat