linux-kernel - Re: [PATCH] Revert "clk: imx: fix composite peripheral flags"

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Date:   Thu, 7 Jan 2021 16:11:58 +0100
From:   Martin Kepplinger <martin.kepplinger@...i.sm>
To:     Abel Vesa <abel.vesa@....com>, Fabio Estevam <festevam@...il.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        linux-clk <linux-clk@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Revert "clk: imx: fix composite peripheral flags"

On 04.01.21 13:05, Abel Vesa wrote:
> On 20-12-31 17:33:40, Fabio Estevam wrote:
>> Hi Martin,
>>
>> On Thu, Dec 31, 2020 at 11:22 AM Martin Kepplinger
>> <martin.kepplinger@...i.sm> wrote:
>>>
>>> This reverts commit 936c383673b9e3007432f17140ac62de53d87db9.
>>>
>>> It breaks clock reparenting via devfreq on the imx8mq used in the
>>> Librem 5 phone. When switching dram frequency (which worked before)
>>> the system now hangs after this where the dram_apb clock cannot be
>>> set:
>>>
>>> [  129.391755] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
>>> set dram_apb parent: -16
>>> [  129.391959] imx8m-ddrc-devfreq 3d400000.memory-controller: ddrc
>>> failed freq switch to 25000000 from 800000000: error -16. now at 25000000
>>> [  129.406133] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
>>> update frequency from PM QoS (-16)
>>
>> I am wondering whether IMX8MQ_CLK_DRAM_ALT should also be marked as
>> CLK_IS_CRITICAL.
>>
> 
> Hmm, the way the DRAM clocks are right registered right now is a real mess.
> The DRAM clocks on i.MX8M are changed in TF-A, but the kernel still needs to
> register them to keep track of the clock tree.
> 
> Martin, I already have a patchset waiting to be shipped which doesn't
> only fix the 8MQ, but all the 8M platforms. Unfortunately, I haven't had the time
> to work on that in the last couple of weeks but I intend to switch back to it soon.
> 
> Fabio, marking the DRAM clocks as critical will not allow the set_parent to be done,
> as CLK_IS_CRITICAL flag and set_parent do not go together. As of now the devfreq
> tries to reparent to be consistent with TF-A configuration.
> 
> My approach here was to make the DRAM clocks read-only. This means adding some
> stuff in the clock core subsystem too.

Hi Abel, thanks a lot for the update. I'm looking forward to seeing your 
patchset.

                               martin