Re: Missing mali regulator in Amlogic dts

From: Christian Hewitt <christianshewitt@gmail.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	"open list:ARM/Amlogic Meson..."
	<linux-amlogic@lists.infradead.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: Missing mali regulator in Amlogic dts
Date: Wed, 9 Mar 2022 09:51:03 +0400	[thread overview]
Message-ID: <907B2B12-F33F-4DF5-8CAA-41CB7766FC78@gmail.com> (raw)
In-Reply-To: <7eec71da-e4b4-eac3-a29c-4244c28f2875@arm.com>

> On 9 Mar 2022, at 12:34 am, Robin Murphy <robin.murphy@arm.com> wrote:
> 
> On 2022-03-08 19:29, Martin Blumenstingl wrote:
>> Hi Heiner,
>> On Tue, Mar 8, 2022 at 7:24 PM Heiner Kallweit <hkallweit1@gmail.com> wrote:
>>> 
>>> I get following error on a  S905W-based system.
>>> lima d00c0000.gpu: dev_pm_opp_set_regulators: no regulator (mali) found: -19
>> This warning is harmless (see below)
>>> I see mali-supply in the DTS of few other vendors, but in no Amlogic DTS.
>>> Is it missing, or are Amlogic SoCs different here?
>> As far as I understand, on GXBB and GXL SoCs the VDDEE regulator is
>> managed by the firmware (which is unfortunately closed-source).
>> IIRC on the hardware side VDDEE is just another PWM regulator, just
>> like with the 32-bit SoCs or with G12A (and later) SoCs.
>>> In the latter case supposedly drivers/gpu/drm/lima/lima_devfreq.c would
>>> have to be changed to check for the optional regulator and not call
>>> devm_pm_opp_set_regulators() if it's missing.
>> I think I just copied the logic from panfrost
>> (drivers/gpu/drm/panfrost/panfrost_devfreq.c) to lima.
>> So GXM boards (using panfrost) will probably report a similar warning.
>> That said, I don't know enough to judge whether your approach makes sense.
> 
> As a quality-of-life thing, it might make the most sense to refactor the API a bit so that it can offer a dedicated helper for setting optional regulators - possibly specifically a single optional regulator, since it's not necessarily clear how optionality should scale to a set of multiple items.

I see occasional (not frequent, but persistent) “error” reports from users with some kind of display related problem, and they look through the boot log and see this and point fingers. It’s harmless, but not showing this on Amlogic devices (all of them show this via lima or panfrost) would be another micro-step towards less distro support effort.

Christian
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