linux-kernel - Re: [PATCH v3 1/2] clk: mediatek: Introduce need_pm_runtime to mtk_clk

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Message-ID: <e0e6febf-1045-49f8-a200-8bc095b0fa50@collabora.com>
Date: Mon, 26 Feb 2024 12:16:10 +0100
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Chen-Yu Tsai <wenst@...omium.org>, Pin-yen Lin <treapking@...omium.org>
Cc: Michael Turquette <mturquette@...libre.com>,
 Stephen Boyd <sboyd@...nel.org>, Matthias Brugger <matthias.bgg@...il.com>,
 Weiyi Lu <weiyi.lu@...iatek.com>, linux-kernel@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-mediatek@...ts.infradead.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/2] clk: mediatek: Introduce need_pm_runtime to
 mtk_clk_desc

Il 23/02/24 05:27, Chen-Yu Tsai ha scritto:
> On Mon, Jan 8, 2024 at 4:18 PM Pin-yen Lin <treapking@...omium.org> wrote:
>>
>> Introduce a new need_pm_runtime variable to mtk_clk_desc to indicate
>> this clock controller needs runtime PM for its operations.
>> Also do a runtime PM get on the clock controller during the
>> probing stage to workaround a possible deadlock.
>>
>> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> 
> Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>
> 
> The patch itself looks fine.
> 
> Besides the MT8183 MFG clock issues, we do actually need this for the
> MT8192 ADSP clock. Its power domain is not enabled by default.
> 

..but on MT8195 the ADSP clock works - because the ADSP node exists.

This poses a question: should we make clock controllers depend on power domains,
or should we keep everything powered off (hence clocks down - no power consumption)
*unless* the user exists?

For the second one, this means that the *device* gets the power domain (adsp), and
not the clock controller (which clocks are effectively useless if there's no user).

Angelo

>> ---
>>
>> Changes in v3:
>> - Update the commit message and the comments before runtime PM call
>>
>> Changes in v2:
>> - Fix the order of error handling
>> - Update the commit message and add a comment before the runtime PM call
>>
>>   drivers/clk/mediatek/clk-mtk.c | 19 +++++++++++++++++++
>>   drivers/clk/mediatek/clk-mtk.h |  2 ++
>>   2 files changed, 21 insertions(+)
>>
>> diff --git a/drivers/clk/mediatek/clk-mtk.c b/drivers/clk/mediatek/clk-mtk.c
>> index 2e55368dc4d8..ba1d1c495bc2 100644
>> --- a/drivers/clk/mediatek/clk-mtk.c
>> +++ b/drivers/clk/mediatek/clk-mtk.c
>> @@ -13,6 +13,7 @@
>>   #include <linux/of.h>
>>   #include <linux/of_address.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
>>   #include <linux/slab.h>
>>
>>   #include "clk-mtk.h"
>> @@ -494,6 +495,18 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
>>                          return IS_ERR(base) ? PTR_ERR(base) : -ENOMEM;
>>          }
>>
>> +
>> +       if (mcd->need_runtime_pm) {
>> +               devm_pm_runtime_enable(&pdev->dev);
>> +               /*
>> +                * Do a pm_runtime_resume_and_get() to workaround a possible
>> +                * deadlock between clk_register() and the genpd framework.
>> +                */
>> +               r = pm_runtime_resume_and_get(&pdev->dev);
>> +               if (r)
>> +                       return r;
>> +       }
>> +
>>          /* Calculate how many clk_hw_onecell_data entries to allocate */
>>          num_clks = mcd->num_clks + mcd->num_composite_clks;
>>          num_clks += mcd->num_fixed_clks + mcd->num_factor_clks;
>> @@ -574,6 +587,9 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
>>                          goto unregister_clks;
>>          }
>>
>> +       if (mcd->need_runtime_pm)
>> +               pm_runtime_put(&pdev->dev);
>> +
>>          return r;
>>
>>   unregister_clks:
>> @@ -604,6 +620,9 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
>>   free_base:
>>          if (mcd->shared_io && base)
>>                  iounmap(base);
>> +
>> +       if (mcd->need_runtime_pm)
>> +               pm_runtime_put(&pdev->dev);
>>          return r;
>>   }
>>
>> diff --git a/drivers/clk/mediatek/clk-mtk.h b/drivers/clk/mediatek/clk-mtk.h
>> index 22096501a60a..c17fe1c2d732 100644
>> --- a/drivers/clk/mediatek/clk-mtk.h
>> +++ b/drivers/clk/mediatek/clk-mtk.h
>> @@ -237,6 +237,8 @@ struct mtk_clk_desc {
>>
>>          int (*clk_notifier_func)(struct device *dev, struct clk *clk);
>>          unsigned int mfg_clk_idx;
>> +
>> +       bool need_runtime_pm;
>>   };
>>
>>   int mtk_clk_pdev_probe(struct platform_device *pdev);
>> --
>> 2.43.0.472.g3155946c3a-goog
>>