linux-kernel - Re: [PATCH] clk: sunxi-ng: ccu-sun4i-a10: Fix mali changing dclk frequency

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Message-ID: <8c2fef37-8eb6-38c6-de3d-547edafac8b7@micronovasrl.com>
Date:   Thu, 1 Feb 2018 17:17:11 +0100
From:   Giulio Benetti <giulio.benetti@...ronovasrl.com>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: sunxi-ng: ccu-sun4i-a10: Fix mali changing dclk
 frequency

Hi,

Il 01/02/2018 13:45, Maxime Ripard ha scritto:
> On Wed, Jan 31, 2018 at 01:05:38PM +0100, Giulio Benetti wrote:
>> Hi,
>>
>> Il 31/01/2018 09:43, Maxime Ripard ha scritto:
>>> Hi,
>>>
>>> On Wed, Jan 31, 2018 at 12:23:59AM +0100, Giulio Benetti wrote:
>>>> When mali.ko is inserted, it set default clocks and call all parent
>>>> clocks to stay into range, causing pll-video0 to change and
>>>> subsequently to change dclk to wrong frequencies.
>>>
>>> This is what you should fix.
>>
>> Ok, so it must be patch title(shrinked of course), right?
>>
>>>
>>>> "gpu" clock has lot of parent plls inside driver, but on sun7i
>>>> pll8-gpu does not depend on pll-video0, pll-ve, pll-video1.
>>>>
>>>> It only depends on 24Mhz main clock.
>>>
>>> I don't really know why you are mentionning that. The GPU clock has
>>> all the parents described in the driver. And the parents' parents are
>>> irrelevant to this particular issue.
>>>
>>>> Remove all pll parents from gpu_parents_sun7i except "pll-gpu".
>>>
>>> However, this is not a proper fix for your issue.
>>
>> Yes, you're right, now I understand.
>>
>> It is more complex than I thought.
>> I need to dig more and study better A20 CCU.
>>
>> So this patch can be dropped.
>>
>>>
>>> What kernel version did you use?
>>
>> Latest mainline.
> 
> I guess this patch could fix it:
> http://code.bulix.org/1kitrq-268936?raw

This should prevent from modifying parent clock.
But my problem was different.
On A20, gpu_clk can have different PLL,
not I've found out the way to choose right one
with assigned-parent-clocks.

I have patchset ready for adding A20 mali node,
but I need some more time to complete with OPP,
then I will submit entire patchset.
Now it works correctly, using right pll(dedicated PLL8),
setting right frequency.

Btw, do I need to add a board using it,
or can I add only Mali node to sun7i-a20.dtsi(plus other little patches)?

> 
> Maxime
> 


-- 
Giulio Benetti
R&D Manager &
Advanced Research

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