linux-kernel - Re: [PATCH] PM / devfreq: Fix build issues with devfreq disabled

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Message-ID: <CAF6AEGud-ESF=VgcaSFzKsWas0H5eSXZDdZGcnd8Ju=pr-W2EQ@mail.gmail.com>
Date:   Tue, 24 Jan 2023 20:31:58 -0800
From:   Rob Clark <robdclark@...il.com>
To:     myungjoo.ham@...sung.com
Cc:     "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "freedreno@...ts.freedesktop.org" <freedreno@...ts.freedesktop.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Rob Clark <robdclark@...omium.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Chia-I Wu <olvaffe@...il.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM / devfreq: Fix build issues with devfreq disabled

On Tue, Jan 24, 2023 at 8:04 PM MyungJoo Ham <myungjoo.ham@...sung.com> wrote:
>
> >Sender : Rob Clark <robdclark@...il.com>
> >Date : 2023-01-24 00:37 (GMT+9)
> >Title : [PATCH] PM / devfreq: Fix build issues with devfreq disabled
> >
> >From: Rob Clark <robdclark@...omium.org>
> >
> >The existing no-op shims for when PM_DEVFREQ (or an individual governor)
> >only do half the job.  The governor specific config/tuning structs need
> >to be available to avoid compile errors in drivers using devfreq.
> >
> >Fixes: 6563f60f14cb ("drm/msm/gpu: Add devfreq tuning debugfs")
> >Signed-off-by: Rob Clark <robdclark@...omium.org>
>
> Doesn't this imply that DRM_MSM should depend on PM_DEVFREQ ?
>
> It appears that gpu/drm/msm/DRM_MSM uses PM_DEVFREQ without actually
> declaring the dependency on PM_DEVFREQ.
> You cannot use SIMPLE_ONDEMAND without DEVFREQ.

Possibly that would resolve some issues, and that might have been my
mistake in assuming that depending on SIMPLE_ONDEMAND implied a
dependency on DEFREQ (which seems like a reasonable assumption, IMHO)

But AFAICT some kernel configs that could otherwise use DRM_MSM don't
support PM_DEVFREQ.. either way, lets solve this properly and remove
needless dependencies on devfreq.

BR,
-R


> Cheers,
> MyungJoo
>
> >---
> >Assuming this doesn't conflict with anything else landing via another
> >tree, an a-b to land this via drm/msm-next would let us un-break builds.
> >(And also start removing "select DEVFREQ_GOV_SIMPLE_ONDEMAND"s added in
> >various places to try to work around this issue.)
> >
> > include/linux/devfreq.h | 7 ++-----
> > 1 file changed, 2 insertions(+), 5 deletions(-)
> >
> >diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> >index 4dc7cda4fd46..7fd704bb8f3d 100644
> >--- a/include/linux/devfreq.h
> >+++ b/include/linux/devfreq.h
> >@@ -273,8 +273,8 @@ void devm_devfreq_unregister_notifier(struct device *dev,
> > struct devfreq *devfreq_get_devfreq_by_node(struct device_node *node);
> > struct devfreq *devfreq_get_devfreq_by_phandle(struct device *dev,
> >                                 const char *phandle_name, int index);
> >+#endif /* CONFIG_PM_DEVFREQ */
> >
> >-#if IS_ENABLED(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND)
> > /**
> >  * struct devfreq_simple_ondemand_data - ``void *data`` fed to struct devfreq
> >  *        and devfreq_add_device
> >@@ -292,9 +292,7 @@ struct devfreq_simple_ondemand_data {
> >         unsigned int upthreshold;
> >         unsigned int downdifferential;
> > };
> >-#endif
> >
> >-#if IS_ENABLED(CONFIG_DEVFREQ_GOV_PASSIVE)
> > enum devfreq_parent_dev_type {
> >         DEVFREQ_PARENT_DEV,
> >         CPUFREQ_PARENT_DEV,
> >@@ -337,9 +335,8 @@ struct devfreq_passive_data {
> >         struct notifier_block nb;
> >         struct list_head cpu_data_list;
> > };
> >-#endif
> >
> >-#else /* !CONFIG_PM_DEVFREQ */
> >+#if !defined(CONFIG_PM_DEVFREQ)
> > static inline struct devfreq *devfreq_add_device(struct device *dev,
> >                                         struct devfreq_dev_profile *profile,
> >                                         const char *governor_name,
> >--
> >2.38.1
> >
>