Messages in this thread Patch in this message | | | Date | Thu, 29 Feb 2024 10:45:27 +0100 | Subject | Re: [PATCH v3 1/2] clk: mediatek: Introduce need_pm_runtime to mtk_clk_desc | From | AngeloGioacchino Del Regno <> |
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Il 29/02/24 08:17, Chen-Yu Tsai ha scritto: > On Mon, Feb 26, 2024 at 7:16 PM AngeloGioacchino Del Regno > <angelogioacchino.delregno@collabora.com> wrote: >> >> Il 23/02/24 05:27, Chen-Yu Tsai ha scritto: >>> On Mon, Jan 8, 2024 at 4:18 PM Pin-yen Lin <treapking@chromium.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@chromium.org> >>> >>> Reviewed-by: Chen-Yu Tsai <wenst@chromium.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. > > That's an indirect dependency that should not be relied on. Say the clock > driver probed but the ADSP hasn't, and you try to read out the current > status. What would happen? > > - Read out works fine, because the power domain is default on, and hasn't > been turned off by late cleanup > - Read out is bogus (but you can't tell) > - Read out hangs. > > The third is what happens on MT8192. There's still some issues on that > front, as even after I applied the ADSP power domain patches from MediaTek, > the readout was still hanging. >
That MT8192 lockup story is getting crazy in my head... anyway, besides that, I get the point - I was somehow ignoring the fact that kernel modules do exist.
Eh, sorry about that :-)
>> 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? > > That's a policy discussion separate from actual hardware dependencies. > *If* the clock controller needs the power domain to be active for the > registers to be accessed, the clock controller *must* have a direct > dependency on the power domain. >
I admit I should've worded that better.
"should we make clock controllers depend on power domains" was actually implying "IF those need one" :-)
I really wonder if - at this point - it's simply a better idea to not restrict the call to devm_pm_runtime_enable/resume_and_get to `need_runtime_pm == true`.
Do we really need to exclude that on other clock controllers that don't have any power domain dependency? Any side effect?
Saying this because if we can avoid yet another per-SoC flag I'm really happy, as readability is also impacted and besides - if we ever find out that one of those need a power domain in the future, we'll need just one commit and just only in the devicetree, instead of enabling a flag in driver X as well as that, avoiding some (potentially unnecessary) noise... I guess.
P.S.: I just noticed that the return value for the devm_pm_runtime_enable() call is not being checked!
......
In short....
Chen-Yu, at this point, do you have any reason why we wouldn't be able and/or it wouldn't be a good idea to just avoid adding the `need_runtime_pm` flag (meaning that we perform pm_runtime calls for all clock drivers unconditionally)?
If this is about longer boot time, I don't think that it's going to be more than a millisecond or two, so that should be completely ignorable.
Can you please do a test for that, or should I?
Cheers Angelo
>> 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). > > No. See my previous paragraph. > > ChenYu > >> 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 >>>> >> >> >>
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