[PATCH] drm/amd: use drm_kms_helper_poll_fini in amdgpu_device_suspend to avoid warning

[Bert Karwatzki]

Am Freitag, dem 24.02.2023 um 02:26 +0000 schrieb Chen, Guchun:
> > Hi Bert,
> > 
> > Thanks for your patch. As we will can drm_kms_helper_poll_enable in
> > resume, so it may not make sense using drm_kms_helper_poll_fini in
> > suspend, from code pairing perspective.
> > 
> > For your case, is it possible to fix the problem by limiting the
> > access of drm_kms_helper_poll_disable with checking
> > mode_config_initialized in adev structure? We can get rid of the
> > code
> > change in drm core in this way.
> > 
> > Regards,
> > Guchun
> > 
> > -----Original Message-----
> > From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of
> > Bert Karwatzki
> > Sent: Friday, February 24, 2023 4:52 AM
> > To: amd-gfx at lists.freedesktop.org
> > Subject: Re: [PATCH] drm/amd: use drm_kms_helper_poll_fini in
> > amdgpu_device_suspend to avoid warning
> > 
> > When drm_kms_helper_poll_disable is used in amdgpu_device_suspend
> > without drm_kms_helper_poll_init having been called it causes a
> > warning in __flush_work:
> > https://gitlab.freedesktop.org/drm/amd/-/issues/2411
> > To avoid this one can use drm_kms_helper_poll_fini instead:
> > Send a second time because Evolution seems to have garbled the
> > first
> > patch. 
> > 
> > From 51cba3ae1e9f557cca8e37eb43b9b9310d0d504d Mon Sep 17 00:00:00
> > 2001
> > From: Bert Karwatzki <spasswolf at web.de>
> > Date: Thu, 16 Feb 2023 10:34:11 +0100
> > Subject: [PATCH] Use drm_kms_helper_poll_fini instead of
> >  drm_kms_helper_poll_disable in amdgpu_device.c to avoid a warning
> > from
> >  __flush_work.
> > 
> > Signed-off-by: Bert Karwatzki <spasswolf at web.de>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
> >  drivers/gpu/drm/drm_probe_helper.c         | 7 ++++---
> >  2 files changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > index b325f7039e0e..dc9e9868a84b 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > @@ -4145,7 +4145,7 @@ int amdgpu_device_suspend(struct drm_device
> > *dev, bool fbcon)
> >         if (amdgpu_acpi_smart_shift_update(dev, AMDGPU_SS_DEV_D3))
> >                 DRM_WARN("smart shift update failed\n");
> >  
> > -       drm_kms_helper_poll_disable(dev);
> > +       drm_kms_helper_poll_fini(dev);
> >  
> >         if (fbcon)
> >                 drm_fb_helper_set_suspend_unlocked(adev_to_drm(adev
> > )-
> > > > fb_helper, true);
> > diff --git a/drivers/gpu/drm/drm_probe_helper.c
> > b/drivers/gpu/drm/drm_probe_helper.c
> > index 8127be134c39..105d00d5ebf3 100644
> > --- a/drivers/gpu/drm/drm_probe_helper.c
> > +++ b/drivers/gpu/drm/drm_probe_helper.c
> > @@ -842,9 +842,10 @@ EXPORT_SYMBOL(drm_kms_helper_is_poll_worker);
> >   *
> >   * This function disables the output polling work.
> >   *
> > - * Drivers can call this helper from their device suspend
> > implementation. It is
> > - * not an error to call this even when output polling isn't
> > enabled
> > or already
> > - * disabled. Polling is re-enabled by calling
> > drm_kms_helper_poll_enable().
> > + * Drivers can call this helper from their device suspend
> > implementation. If it
> > + * is not known if drm_kms_helper_poll_init has been called before
> > the
> > driver
> > + * should use drm_kms_helper_poll_fini_instead.
> > + * Polling is re-enabled by calling drm_kms_helper_poll_enable().
> >   *
> >   * Note that calls to enable and disable polling must be strictly
> > ordered, which
> >   * is automatically the case when they're only call from
> > suspend/resume
> > 
No, that does not work for me. I tried (in linux-next-20230224):

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index c4a4e2fe6681..27fb42b1bde4 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -4145,7 +4145,13 @@ int amdgpu_device_suspend(struct drm_device
*dev, bool fbcon)
        if (amdgpu_acpi_smart_shift_update(dev, AMDGPU_SS_DEV_D3))
                DRM_WARN("smart shift update failed\n");
 
-       drm_kms_helper_poll_disable(dev);
+       if (adev->mode_info.mode_config_initialized) {
+               printk(KERN_INFO "adev-
> mode_info.mode_config_initialized = %d\n",
+                               adev-
> mode_info.mode_config_initialized);
+               printk(KERN_INFO "dev->mode_config.poll_enabled =
%d\n",
+                               dev->mode_config.poll_enabled);
+               drm_kms_helper_poll_disable(dev);
+       }
 
        if (fbcon)
                drm_fb_helper_set_suspend_unlocked(adev_to_drm(adev)-
> fb_helper, true);

and found that mode_config_initialized=1 but dev-
> mode_config.poll_enabled=0 with the usual warning:
[   23.287058] adev->mode_info.mode_config_initialized = 1
[   23.287061] dev->mode_config.poll_enabled = 0
[   23.287063] ------------[ cut here ]------------
[   23.287064] WARNING: CPU: 0 PID: 16 at kernel/workqueue.c:3167
__flush_work.isra.0+0x261/0x270

The flag that needs to be checked to avoid the warning is dev-
> mode_config.poll_enabled which gets set by drm_kms_helper_poll_init
and drm_kms_helper_poll_fini does just that. Changing the comment of
drms_kms_helper_poll_disable is technically not necessary though.
(resent because this mail didn't appear in the archive of amd-gfx
so I thought it might have been lost)
Bert Karwatzki