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Message-Id: <201006172114.19033.rjw@sisk.pl>
Date: Thu, 17 Jun 2010 21:14:18 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Alex Deucher <alexdeucher@...il.com>
Cc: Ondrej Zary <linux@...nbow-software.org>,
Dave Airlie <airlied@...hat.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
"dri-devel" <dri-devel@...ts.freedesktop.org>
Subject: Re: [Regression, post-2.6.34] Hibernation broken on machines with radeon/KMS and r300
On Thursday, June 17, 2010, Alex Deucher wrote:
> 2010/6/17 Rafael J. Wysocki <rjw@...k.pl>:
> > On Wednesday, June 16, 2010, Alex Deucher wrote:
> >> On Wed, Jun 16, 2010 at 4:16 PM, Rafael J. Wysocki <rjw@...k.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@...k.pl> wrote:
> >> >> > > > > On Monday, June 14, 2010, Alex Deucher wrote:
> >> >> > > > >> On Mon, Jun 14, 2010 at 10:53 AM, Rafael J. Wysocki <rjw@...k.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?
Do you mean the $subject one? Yes, it does.
Rafael
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.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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