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SubjectRe: [Regression, post-2.6.34] Hibernation broken on machines with radeon/KMS and r300
From
2010/6/17 Rafael J. Wysocki <rjw@sisk.pl>:
> On Wednesday, June 16, 2010, Alex Deucher wrote:
>> On Wed, Jun 16, 2010 at 4:16 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
>> > On Wednesday, June 16, 2010, Ondrej Zary wrote:
>> >> On Wednesday 16 June 2010, Rafael J. Wysocki wrote:
>> >> > On Tuesday, June 15, 2010, Rafael J. Wysocki wrote:
>> >> > > On Monday, June 14, 2010, Alex Deucher wrote:
>> >> > > > On Mon, Jun 14, 2010 at 3:03 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
>> >> > > > > On Monday, June 14, 2010, Alex Deucher wrote:
>> >> > > > >> On Mon, Jun 14, 2010 at 10:53 AM, Rafael J. Wysocki <rjw@sisk.pl>
>> >> wrote:
>> >> > > > >> > Alex, Dave,
>> >> > > > >> >
>> >> > > > >> > I'm afraid hibernation is broken on all machines using radeon/KMS
>> >> > > > >> > with r300 after commit ce8f53709bf440100cb9d31b1303291551cf517f
>> >> > > > >> > (drm/radeon/kms/pm: rework power management).  At least, I'm able
>> >> > > > >> > to reproduce the symptom, which is that the machine hangs hard
>> >> > > > >> > around the point where an image is created (probably during the
>> >> > > > >> > device thaw phase), on two different boxes with r300 (the output
>> >> > > > >> > of lspci from one of them is attached for reference, the other one
>> >> > > > >> > is HP nx6325).
>> >> > > > >> >
>> >> > > > >> > Suspend to RAM appears to work fine at least on one of the
>> >> > > > >> > affected boxes.
>> >> > > > >> >
>> >> > > > >> > Unfortunately, the commit above changes a lot of code and it's not
>> >> > > > >> > too easy to figure out what's wrong with it and I didn't have the
>> >> > > > >> > time to look more into details of this failure.  However, it looks
>> >> > > > >> > like you use .suspend() and .resume() callbacks as .freeze() and
>> >> > > > >> > .thaw() which may not be 100% correct (in fact it looks like the
>> >> > > > >> > "legacy" PCI suspend/resume is used, which is not recommended any
>> >> > > > >> > more).
>> >> > > > >>
>> >> > > > >> Does it work any better after Dave's last drm pull request?
>> >> > > > >
>> >> > > > > Nope.  The symptom is slightly different, though, because now it
>> >> > > > > hangs after turning off the screen.
>> >> > > > >
>> >> > > > >> With the latest changes, pm should not be a factor unless it's
>> >> > > > >> explicitly enabled via sysfs.
>> >> > > > >
>> >> > > > > Well, I guess the first pm patch changed more than just pm, then.
>> >> > > >
>> >> > > > Does this patch help?
>> >> > > > http://lists.freedesktop.org/archives/dri-devel/2010-June/001314.html
>> >> > >
>> >> > > No, it doesn't.  I try to hibernate, everything works to the point where
>> >> > > the screen goes off and the box hangs (solid).  Normally, it would turn
>> >> > > the screen back on and continue with saving the image.
>> >> > >
>> >> > > But, since that happens with the patch above applied, I think it doesn't
>> >> > > really pass the suspend phase (IOW, it probably hangs somewhere in the
>> >> > > radeon's suspend routine).
>> >> >
>> >> > I've just verified that in fact hibernation works on HP nx6325 with
>> >> > 2.6.35-rc3, but it takes about 55 sec. to suspend the graphics adapter in
>> >> > the "freeze" phase.  Surprisingly enough, during suspend to RAM it works
>> >> > normally (as well as in the "poweroff" phase of hibernation).
>> >>
>> >> It takes 2 minutes on RV530:
>> >> https://bugzilla.redhat.com/show_bug.cgi?id=586522
>> >
>> > Well, my second affected box appears to hang somewhere in the radeon's suspend
>> > routine.
>>
>> Does the attached patch help?
>
> It helps, but from what I can see in the code, it still has a few problems.
>
> First, the mutex around cancel_delayed_work() in radeon_pm_suspend()
> doesn't really serve any purpose, because rdev->pm.pm_method cannot change
> at this point and cancel_delayed_work() only tries to delete the work's timer.
> Moreover, it doesn't prevent the work handler from running, in which case the
> handler can do some wrong things and will rearm itself to do some more wrong
> things going forward.  So, I think it's better to wait for the handler to run in case it's
> already been queued up and it should also be prevented from rearming itself in
> that case.
>
> Second, in radeon_set_pm_method() the cancel_delayed_work() is not sufficient
> to prevent the work handler from running and queing up itself for the next run
> (the failure scenario is that cancel_delayed_work_sync() returns 0, so the
> handler is run, it waits on the mutex and then rearms itself after the mutex
> has been released), so it looks like cancel_delayed_work_sync()
> should be used to make sure it's not going to run again, but calling
> that cancel_delayed_work_sync() from under the mutex is not a good idea.
>
> Finally, there's a potential deadlock in radeon_pm_fini(), where
> cancel_delayed_work_sync() is called under rdev->pm.mutex, but the
> work handler tries to acquire the same mutex (if it wins the race).
>
> So, I think something like the appended patch is needed.
>

Looks reasonable. Does it fix the suspend issue?

Alex

> Rafael
>
>
> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> ---
>  drivers/gpu/drm/radeon/radeon.h    |    3 +-
>  drivers/gpu/drm/radeon/radeon_pm.c |   41 ++++++++++++++++++++++++++++++-------
>  2 files changed, 36 insertions(+), 8 deletions(-)
>
> Index: linux-2.6/drivers/gpu/drm/radeon/radeon_pm.c
> ===================================================================
> --- linux-2.6.orig/drivers/gpu/drm/radeon/radeon_pm.c
> +++ linux-2.6/drivers/gpu/drm/radeon/radeon_pm.c
> @@ -397,13 +397,20 @@ static ssize_t radeon_set_pm_method(stru
>                rdev->pm.dynpm_planned_action = DYNPM_ACTION_DEFAULT;
>                mutex_unlock(&rdev->pm.mutex);
>        } else if (strncmp("profile", buf, strlen("profile")) == 0) {
> +               bool flush_wq = false;
> +
>                mutex_lock(&rdev->pm.mutex);
> -               rdev->pm.pm_method = PM_METHOD_PROFILE;
> +               if (rdev->pm.pm_method == PM_METHOD_DYNPM) {
> +                       cancel_delayed_work(&rdev->pm.dynpm_idle_work);
> +                       flush_wq = true;
> +               }
>                /* disable dynpm */
>                rdev->pm.dynpm_state = DYNPM_STATE_DISABLED;
>                rdev->pm.dynpm_planned_action = DYNPM_ACTION_NONE;
> -               cancel_delayed_work(&rdev->pm.dynpm_idle_work);
> +               rdev->pm.pm_method = PM_METHOD_PROFILE;
>                mutex_unlock(&rdev->pm.mutex);
> +               if (flush_wq)
> +                       flush_workqueue(rdev->wq);
>        } else {
>                DRM_ERROR("invalid power method!\n");
>                goto fail;
> @@ -418,9 +425,18 @@ static DEVICE_ATTR(power_method, S_IRUGO
>
>  void radeon_pm_suspend(struct radeon_device *rdev)
>  {
> +       bool flush_wq = false;
> +
>        mutex_lock(&rdev->pm.mutex);
> -       cancel_delayed_work(&rdev->pm.dynpm_idle_work);
> +       if (rdev->pm.pm_method == PM_METHOD_DYNPM) {
> +               cancel_delayed_work(&rdev->pm.dynpm_idle_work);
> +               if (rdev->pm.dynpm_state == DYNPM_STATE_ACTIVE)
> +                       rdev->pm.dynpm_state = DYNPM_STATE_SUSPENDED;
> +               flush_wq = true;
> +       }
>        mutex_unlock(&rdev->pm.mutex);
> +       if (flush_wq)
> +               flush_workqueue(rdev->wq);
>  }
>
>  void radeon_pm_resume(struct radeon_device *rdev)
> @@ -432,6 +448,12 @@ void radeon_pm_resume(struct radeon_devi
>        rdev->pm.current_sclk = rdev->clock.default_sclk;
>        rdev->pm.current_mclk = rdev->clock.default_mclk;
>        rdev->pm.current_vddc = rdev->pm.power_state[rdev->pm.default_power_state_index].clock_info[0].voltage.voltage;
> +       if (rdev->pm.pm_method == PM_METHOD_DYNPM
> +           && rdev->pm.dynpm_state == DYNPM_STATE_SUSPENDED) {
> +               rdev->pm.dynpm_state = DYNPM_STATE_ACTIVE;
> +               queue_delayed_work(rdev->wq, &rdev->pm.dynpm_idle_work,
> +                                       msecs_to_jiffies(RADEON_IDLE_LOOP_MS));
> +       }
>        mutex_unlock(&rdev->pm.mutex);
>        radeon_pm_compute_clocks(rdev);
>  }
> @@ -486,6 +508,8 @@ int radeon_pm_init(struct radeon_device
>  void radeon_pm_fini(struct radeon_device *rdev)
>  {
>        if (rdev->pm.num_power_states > 1) {
> +               bool flush_wq = false;
> +
>                mutex_lock(&rdev->pm.mutex);
>                if (rdev->pm.pm_method == PM_METHOD_PROFILE) {
>                        rdev->pm.profile = PM_PROFILE_DEFAULT;
> @@ -493,13 +517,16 @@ void radeon_pm_fini(struct radeon_device
>                        radeon_pm_set_clocks(rdev);
>                } else if (rdev->pm.pm_method == PM_METHOD_DYNPM) {
>                        /* cancel work */
> -                       cancel_delayed_work_sync(&rdev->pm.dynpm_idle_work);
> +                       cancel_delayed_work(&rdev->pm.dynpm_idle_work);
> +                       flush_wq = true;
>                        /* reset default clocks */
>                        rdev->pm.dynpm_state = DYNPM_STATE_DISABLED;
>                        rdev->pm.dynpm_planned_action = DYNPM_ACTION_DEFAULT;
>                        radeon_pm_set_clocks(rdev);
>                }
>                mutex_unlock(&rdev->pm.mutex);
> +               if (flush_wq)
> +                       flush_workqueue(rdev->wq);
>
>                device_remove_file(rdev->dev, &dev_attr_power_profile);
>                device_remove_file(rdev->dev, &dev_attr_power_method);
> @@ -720,12 +747,12 @@ static void radeon_dynpm_idle_work_handl
>                        radeon_pm_get_dynpm_state(rdev);
>                        radeon_pm_set_clocks(rdev);
>                }
> +
> +               queue_delayed_work(rdev->wq, &rdev->pm.dynpm_idle_work,
> +                                       msecs_to_jiffies(RADEON_IDLE_LOOP_MS));
>        }
>        mutex_unlock(&rdev->pm.mutex);
>        ttm_bo_unlock_delayed_workqueue(&rdev->mman.bdev, resched);
> -
> -       queue_delayed_work(rdev->wq, &rdev->pm.dynpm_idle_work,
> -                                       msecs_to_jiffies(RADEON_IDLE_LOOP_MS));
>  }
>
>  /*
> Index: linux-2.6/drivers/gpu/drm/radeon/radeon.h
> ===================================================================
> --- linux-2.6.orig/drivers/gpu/drm/radeon/radeon.h
> +++ linux-2.6/drivers/gpu/drm/radeon/radeon.h
> @@ -619,7 +619,8 @@ enum radeon_dynpm_state {
>        DYNPM_STATE_DISABLED,
>        DYNPM_STATE_MINIMUM,
>        DYNPM_STATE_PAUSED,
> -       DYNPM_STATE_ACTIVE
> +       DYNPM_STATE_ACTIVE,
> +       DYNPM_STATE_SUSPENDED,
>  };
>  enum radeon_dynpm_action {
>        DYNPM_ACTION_NONE,
>
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