Messages in this thread | ![/](/images/icornerl.gif) | | From | Chen-Yu Tsai <> | Date | Thu, 29 Feb 2024 18:34:03 +0800 | Subject | Re: [PATCH v3 1/2] clk: mediatek: Introduce need_pm_runtime to mtk_clk_desc |
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On Thu, Feb 29, 2024 at 5:45 PM AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> wrote: > > 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.
I think it's just more of a "don't enable features you don't need" thing. We already ran into a weird deadlock, which is why the devm_pm_runtime_enable() call has that comment.
I don't think anyone has actually looked at it. As you said it shouldn't be much, at least during boot time. It's one call per clock controller.
> Can you please do a test for that, or should I?
The earliest I can work on it would be some time next week. Does that work for you?
ChenYu
> 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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