Re: [PATCH 07/10] drm/radeon: apply Murphy's law to the kms irq code

["Christian König" <deathsimple@vodafone.de>]

On 31.05.2012 20:15, Alex Deucher wrote:
> On Thu, May 24, 2012 at 11:35 AM, Alex Deucher<alexdeucher@gmail.com>  wrote:
>> On Thu, May 24, 2012 at 3:49 AM, Christian König
>> <deathsimple@vodafone.de>  wrote:
>>> From: Christian Koenig<christian.koenig@amd.com>
>>>
>>> 1. It is really dangerous to have more than one
>>>    spinlock protecting the same information.
>>>
>>> 2. radeon_irq_set sometimes wasn't called with lock
>>>    protection, so it can happen that more than one
>>>    CPU would tamper with the irq regs at the same
>>>    time.
>>>
>>> 3. The pm.gui_idle variable was assuming that the 3D
>>>    engine wasn't becoming idle between testing the
>>>    register and setting the variable. So just remove
>>>    it and test the register directly.
>>>
>>> Signed-off-by: Christian Koenig<christian.koenig@amd.com>
>>> ---
>>>   drivers/gpu/drm/radeon/evergreen.c      |    1 -
>>>   drivers/gpu/drm/radeon/r100.c           |    1 -
>>>   drivers/gpu/drm/radeon/r600.c           |    1 -
>>>   drivers/gpu/drm/radeon/r600_hdmi.c      |    6 +--
>>>   drivers/gpu/drm/radeon/radeon.h         |   33 +++++++-------
>>>   drivers/gpu/drm/radeon/radeon_irq_kms.c |   72 +++++++++++++++++++++++++------
>>>   drivers/gpu/drm/radeon/radeon_kms.c     |   12 ++++--
>>>   drivers/gpu/drm/radeon/radeon_pm.c      |   12 +-----
>>>   drivers/gpu/drm/radeon/rs600.c          |    1 -
>>>   drivers/gpu/drm/radeon/si.c             |    1 -
>>>   10 files changed, 90 insertions(+), 50 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
>>> index bfcb39e..9e9b3bb 100644
>>> --- a/drivers/gpu/drm/radeon/evergreen.c
>>> +++ b/drivers/gpu/drm/radeon/evergreen.c
>>> @@ -3254,7 +3254,6 @@ restart_ih:
>>>                         break;
>>>                 case 233: /* GUI IDLE */
>>>                         DRM_DEBUG("IH: GUI idle\n");
>>> -                       rdev->pm.gui_idle = true;
>>>                         wake_up(&rdev->irq.idle_queue);
>>>                         break;
>>>                 default:
>>> diff --git a/drivers/gpu/drm/radeon/r100.c b/drivers/gpu/drm/radeon/r100..c
>>> index 415b7d8..2587426 100644
>>> --- a/drivers/gpu/drm/radeon/r100.c
>>> +++ b/drivers/gpu/drm/radeon/r100.c
>>> @@ -782,7 +782,6 @@ int r100_irq_process(struct radeon_device *rdev)
>>>                 /* gui idle interrupt */
>>>                 if (status&  RADEON_GUI_IDLE_STAT) {
>>>                         rdev->irq.gui_idle_acked = true;
>>> -                       rdev->pm.gui_idle = true;
>>>                         wake_up(&rdev->irq.idle_queue);
>>>                 }
>>>                 /* Vertical blank interrupts */
>>> diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600..c
>>> index eadbb06..90c6639 100644
>>> --- a/drivers/gpu/drm/radeon/r600.c
>>> +++ b/drivers/gpu/drm/radeon/r600.c
>>> @@ -3542,7 +3542,6 @@ restart_ih:
>>>                         break;
>>>                 case 233: /* GUI IDLE */
>>>                         DRM_DEBUG("IH: GUI idle\n");
>>> -                       rdev->pm.gui_idle = true;
>>>                         wake_up(&rdev->irq.idle_queue);
>>>                         break;
>>>                 default:
>>> diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c
>>> index 226379e..b76c0f2 100644
>>> --- a/drivers/gpu/drm/radeon/r600_hdmi.c
>>> +++ b/drivers/gpu/drm/radeon/r600_hdmi.c
>>> @@ -523,8 +523,7 @@ void r600_hdmi_enable(struct drm_encoder *encoder)
>>>
>>>         if (rdev->irq.installed) {
>>>                 /* if irq is available use it */
>>> -               rdev->irq.afmt[dig->afmt->id] = true;
>>> -               radeon_irq_set(rdev);
>>> +               radeon_irq_kms_enable_afmt(rdev, dig->afmt->id);
>>>         }
>>>
>>>         dig->afmt->enabled = true;
>>> @@ -560,8 +559,7 @@ void r600_hdmi_disable(struct drm_encoder *encoder)
>>>                   offset, radeon_encoder->encoder_id);
>>>
>>>         /* disable irq */
>>> -       rdev->irq.afmt[dig->afmt->id] = false;
>>> -       radeon_irq_set(rdev);
>>> +       radeon_irq_kms_disable_afmt(rdev, dig->afmt->id);
>>>
>>>         /* Older chipsets not handled by AtomBIOS */
>>>         if (rdev->family>= CHIP_R600&&  !ASIC_IS_DCE3(rdev)) {
>>> diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
>>> index 8479096..23552b4 100644
>>> --- a/drivers/gpu/drm/radeon/radeon.h
>>> +++ b/drivers/gpu/drm/radeon/radeon.h
>>> @@ -610,21 +610,20 @@ union radeon_irq_stat_regs {
>>>   #define RADEON_MAX_AFMT_BLOCKS 6
>>>
>>>   struct radeon_irq {
>>> -       bool            installed;
>>> -       bool            sw_int[RADEON_NUM_RINGS];
>>> -       bool            crtc_vblank_int[RADEON_MAX_CRTCS];
>>> -       bool            pflip[RADEON_MAX_CRTCS];
>>> -       wait_queue_head_t       vblank_queue;
>>> -       bool            hpd[RADEON_MAX_HPD_PINS];
>>> -       bool            gui_idle;
>>> -       bool            gui_idle_acked;
>>> -       wait_queue_head_t       idle_queue;
>>> -       bool            afmt[RADEON_MAX_AFMT_BLOCKS];
>>> -       spinlock_t sw_lock;
>>> -       int sw_refcount[RADEON_NUM_RINGS];
>>> -       union radeon_irq_stat_regs stat_regs;
>>> -       spinlock_t pflip_lock[RADEON_MAX_CRTCS];
>>> -       int pflip_refcount[RADEON_MAX_CRTCS];
>>> +       bool                            installed;
>>> +       spinlock_t                      lock;
>>> +       bool                            sw_int[RADEON_NUM_RINGS];
>>> +       int                             sw_refcount[RADEON_NUM_RINGS];
>>> +       bool                            crtc_vblank_int[RADEON_MAX_CRTCS];
>>> +       bool                            pflip[RADEON_MAX_CRTCS];
>>> +       int                             pflip_refcount[RADEON_MAX_CRTCS];
>>> +       wait_queue_head_t               vblank_queue;
>>> +       bool                            hpd[RADEON_MAX_HPD_PINS];
>>> +       bool                            gui_idle;
>>> +       bool                            gui_idle_acked;
>>> +       wait_queue_head_t               idle_queue;
>>> +       bool                            afmt[RADEON_MAX_AFMT_BLOCKS];
>>> +       union radeon_irq_stat_regs      stat_regs;
>>>   };
>>>
>>>   int radeon_irq_kms_init(struct radeon_device *rdev);
>>> @@ -633,6 +632,9 @@ void radeon_irq_kms_sw_irq_get(struct radeon_device *rdev, int ring);
>>>   void radeon_irq_kms_sw_irq_put(struct radeon_device *rdev, int ring);
>>>   void radeon_irq_kms_pflip_irq_get(struct radeon_device *rdev, int crtc);
>>>   void radeon_irq_kms_pflip_irq_put(struct radeon_device *rdev, int crtc);
>>> +void radeon_irq_kms_enable_afmt(struct radeon_device *rdev, int block);
>>> +void radeon_irq_kms_disable_afmt(struct radeon_device *rdev, int block);
>>> +int radeon_irq_kms_wait_gui_idle(struct radeon_device *rdev);
>>>
>>>   /*
>>>   * CP&  rings.
>>> @@ -1058,7 +1060,6 @@ struct radeon_pm {
>>>         int                     active_crtc_count;
>>>         int                     req_vblank;
>>>         bool                    vblank_sync;
>>> -       bool                    gui_idle;
>>>         fixed20_12              max_bandwidth;
>>>         fixed20_12              igp_sideport_mclk;
>>>         fixed20_12              igp_system_mclk;
>>> diff --git a/drivers/gpu/drm/radeon/radeon_irq_kms.c b/drivers/gpu/drm/radeon/radeon_irq_kms.c
>>> index 5df58d1..11fc4f7 100644
>>> --- a/drivers/gpu/drm/radeon/radeon_irq_kms.c
>>> +++ b/drivers/gpu/drm/radeon/radeon_irq_kms.c
>>> @@ -32,6 +32,8 @@
>>>   #include "radeon.h"
>>>   #include "atom.h"
>>>
>>> +#define RADEON_WAIT_IDLE_TIMEOUT 200
>>> +
>>>   irqreturn_t radeon_driver_irq_handler_kms(DRM_IRQ_ARGS)
>>>   {
>>>         struct drm_device *dev = (struct drm_device *) arg;
>>> @@ -62,8 +64,10 @@ static void radeon_hotplug_work_func(struct work_struct *work)
>>>   void radeon_driver_irq_preinstall_kms(struct drm_device *dev)
>>>   {
>>>         struct radeon_device *rdev = dev->dev_private;
>>> +       unsigned long irqflags;
>>>         unsigned i;
>>>
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         /* Disable *all* interrupts */
>>>         for (i = 0; i<  RADEON_NUM_RINGS; i++)
>>>                 rdev->irq.sw_int[i] = false;
>>> @@ -76,6 +80,7 @@ void radeon_driver_irq_preinstall_kms(struct drm_device *dev)
>>>                 rdev->irq.afmt[i] = false;
>>>         }
>>>         radeon_irq_set(rdev);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>         /* Clear bits */
>>>         radeon_irq_process(rdev);
>>>   }
>>> @@ -83,23 +88,28 @@ void radeon_driver_irq_preinstall_kms(struct drm_device *dev)
>>>   int radeon_driver_irq_postinstall_kms(struct drm_device *dev)
>>>   {
>>>         struct radeon_device *rdev = dev->dev_private;
>>> +       unsigned long irqflags;
>>>         unsigned i;
>>>
>>>         dev->max_vblank_count = 0x001fffff;
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         for (i = 0; i<  RADEON_NUM_RINGS; i++)
>>>                 rdev->irq.sw_int[i] = true;
>>>         radeon_irq_set(rdev);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>         return 0;
>>>   }
>>>
>>>   void radeon_driver_irq_uninstall_kms(struct drm_device *dev)
>>>   {
>>>         struct radeon_device *rdev = dev->dev_private;
>>> +       unsigned long irqflags;
>>>         unsigned i;
>>>
>>>         if (rdev == NULL) {
>>>                 return;
>>>         }
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         /* Disable *all* interrupts */
>>>         for (i = 0; i<  RADEON_NUM_RINGS; i++)
>>>                 rdev->irq.sw_int[i] = false;
>>> @@ -112,6 +122,7 @@ void radeon_driver_irq_uninstall_kms(struct drm_device *dev)
>>>                 rdev->irq.afmt[i] = false;
>>>         }
>>>         radeon_irq_set(rdev);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>   }
>>>
>>>   static bool radeon_msi_ok(struct radeon_device *rdev)
>>> @@ -168,15 +179,12 @@ static bool radeon_msi_ok(struct radeon_device *rdev)
>>>
>>>   int radeon_irq_kms_init(struct radeon_device *rdev)
>>>   {
>>> -       int i;
>>>         int r = 0;
>>>
>>>         INIT_WORK(&rdev->hotplug_work, radeon_hotplug_work_func);
>>>         INIT_WORK(&rdev->audio_work, r600_audio_update_hdmi);
>>>
>>> -       spin_lock_init(&rdev->irq.sw_lock);
>>> -       for (i = 0; i<  rdev->num_crtc; i++)
>>> -               spin_lock_init(&rdev->irq.pflip_lock[i]);
>>> +       spin_lock_init(&rdev->irq.lock);
>>>         r = drm_vblank_init(rdev->ddev, rdev->num_crtc);
>>>         if (r) {
>>>                 return r;
>>> @@ -217,25 +225,25 @@ void radeon_irq_kms_sw_irq_get(struct radeon_device *rdev, int ring)
>>>   {
>>>         unsigned long irqflags;
>>>
>>> -       spin_lock_irqsave(&rdev->irq.sw_lock, irqflags);
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         if (rdev->ddev->irq_enabled&&  (++rdev->irq.sw_refcount[ring] == 1)) {
>>>                 rdev->irq.sw_int[ring] = true;
>>>                 radeon_irq_set(rdev);
>>>         }
>>> -       spin_unlock_irqrestore(&rdev->irq.sw_lock, irqflags);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>   }
>>>
>>>   void radeon_irq_kms_sw_irq_put(struct radeon_device *rdev, int ring)
>>>   {
>>>         unsigned long irqflags;
>>>
>>> -       spin_lock_irqsave(&rdev->irq.sw_lock, irqflags);
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         BUG_ON(rdev->ddev->irq_enabled&&  rdev->irq.sw_refcount[ring]<= 0);
>>>         if (rdev->ddev->irq_enabled&&  (--rdev->irq.sw_refcount[ring] == 0)) {
>>>                 rdev->irq.sw_int[ring] = false;
>>>                 radeon_irq_set(rdev);
>>>         }
>>> -       spin_unlock_irqrestore(&rdev->irq.sw_lock, irqflags);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>   }
>>>
>>>   void radeon_irq_kms_pflip_irq_get(struct radeon_device *rdev, int crtc)
>>> @@ -245,12 +253,12 @@ void radeon_irq_kms_pflip_irq_get(struct radeon_device *rdev, int crtc)
>>>         if (crtc<  0 || crtc>= rdev->num_crtc)
>>>                 return;
>>>
>>> -       spin_lock_irqsave(&rdev->irq.pflip_lock[crtc], irqflags);
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         if (rdev->ddev->irq_enabled&&  (++rdev->irq.pflip_refcount[crtc] == 1)) {
>>>                 rdev->irq.pflip[crtc] = true;
>>>                 radeon_irq_set(rdev);
>>>         }
>>> -       spin_unlock_irqrestore(&rdev->irq.pflip_lock[crtc], irqflags);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>   }
>>>
>>>   void radeon_irq_kms_pflip_irq_put(struct radeon_device *rdev, int crtc)
>>> @@ -260,12 +268,52 @@ void radeon_irq_kms_pflip_irq_put(struct radeon_device *rdev, int crtc)
>>>         if (crtc<  0 || crtc>= rdev->num_crtc)
>>>                 return;
>>>
>>> -       spin_lock_irqsave(&rdev->irq.pflip_lock[crtc], irqflags);
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>>         BUG_ON(rdev->ddev->irq_enabled&&  rdev->irq.pflip_refcount[crtc]<= 0);
>>>         if (rdev->ddev->irq_enabled&&  (--rdev->irq.pflip_refcount[crtc] == 0)) {
>>>                 rdev->irq.pflip[crtc] = false;
>>>                 radeon_irq_set(rdev);
>>>         }
>>> -       spin_unlock_irqrestore(&rdev->irq.pflip_lock[crtc], irqflags);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>> +}
>>> +
>>> +void radeon_irq_kms_enable_afmt(struct radeon_device *rdev, int block)
>>> +{
>>> +       unsigned long irqflags;
>>> +
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>> +       rdev->irq.afmt[block] = true;
>>> +       radeon_irq_set(rdev);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>> +
>>> +}
>>> +
>>> +void radeon_irq_kms_disable_afmt(struct radeon_device *rdev, int block)
>>> +{
>>> +       unsigned long irqflags;
>>> +
>>> +       spin_lock_irqsave(&rdev->irq.lock, irqflags);
>>> +       rdev->irq.afmt[block] = false;
>>> +       radeon_irq_set(rdev);
>>> +       spin_unlock_irqrestore(&rdev->irq.lock, irqflags);
>>>   }
>>>
>> Should probably also add radeon_irq_kms_[en|dis]able_hpd() function
>> and call replaced the calls to *_irq_set() in the *_hpd_init() and
>> *_hpd_fini() callbacks for display hotplug.
> See attached follow on patch.
The version I pushed into my repo includes nearly the same 
implementation in the v2 version of the patch. I just haven't had time 
to send it to the list yet.

There also is a V2 of the IH patch. After removing the spinlock (and 
with it the disabling of IRQs) in the interrupt handler we seem to hit a 
race condition in the vblank code. Actually I think we can hit the same 
problem when the IH is currently running on one CPU and X modifying 
vblank properties on another CPU, but that is really really really unlikely.

Whatever it is I modified the IH patch to keep the spinlock for now, put 
I think I should look into it more closely.

Anyway going to send out the patches in a minute,
Christian.