Re: [Intel-gfx] [PATCH v2 02/21] drm: Evaluate struct drm_device.vblank_disable_immediate on each use

[Thomas Zimmermann]

Hi

Am 15.01.20 um 15:37 schrieb Ville Syrjälä:
> On Wed, Jan 15, 2020 at 01:16:33PM +0100, Thomas Zimmermann wrote:
>> VBLANK interrupts can be disabled immediately or with a delay, where the
>> latter is the default. The former option can be selected by setting
>> get_vblank_timestamp, and enabling vblank_disable_immediate in struct
>> drm_device.
>>
>> The setup is only evaluated once when DRM initializes VBLANKs. Evaluating
>> the settings on each use of vblank_disable_immediate will allow for easy
>> integration of CRTC VBLANK functions.
>>
>> Signed-off-by: Thomas Zimmermann 
>> ---
>>  drivers/gpu/drm/drm_vblank.c | 31 ++-
>>  1 file changed, 14 insertions(+), 17 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
>> index 3f1dd54cc8bb..abb085c67d82 100644
>> --- a/drivers/gpu/drm/drm_vblank.c
>> +++ b/drivers/gpu/drm/drm_vblank.c
>> @@ -481,19 +481,6 @@ int drm_vblank_init(struct drm_device *dev, unsigned 
>> int num_crtcs)
>>  
>>  DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
>>  
>> -/* Driver specific high-precision vblank timestamping supported? */
>> -if (dev->driver->get_vblank_timestamp)
>> -DRM_INFO("Driver supports precise vblank timestamp query.\n");
>> -else
>> -DRM_INFO("No driver support for vblank timestamp query.\n");
>> -
>> -/* Must have precise timestamping for reliable vblank instant disable */
>> -if (dev->vblank_disable_immediate && 
>> !dev->driver->get_vblank_timestamp) {
>> -dev->vblank_disable_immediate = false;
>> -DRM_INFO("Setting vblank_disable_immediate to false because "
>> - "get_vblank_timestamp == NULL\n");
>> -}
> 
> Which drivers are so broken they set vblank_disable_immediate to true
> without having the vfunc specified? IMO this code should just go away
> (or converted to a WARN).

It's probably not a problem in practice. I'll put WARN_ON around the
condition.

Best regards
Thomas

> 
>> -
>>  return 0;
>>  
>>  err:
>> @@ -1070,6 +1057,15 @@ int drm_crtc_vblank_get(struct drm_crtc *crtc)
>>  }
>>  EXPORT_SYMBOL(drm_crtc_vblank_get);
>>  
>> +static bool __vblank_disable_immediate(struct drm_device *dev, unsigned int 
>> pipe)
>> +{
>> +if (!dev->vblank_disable_immediate)
>> +return false;
>> +if (!dev->driver->get_vblank_timestamp)
>> +return false;
>> +return true;
>> +}
>> +
>>  static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
>>  {
>>  struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
>> @@ -1086,7 +1082,7 @@ static void drm_vblank_put(struct drm_device *dev, 
>> unsigned int pipe)
>>  return;
>>  else if (drm_vblank_offdelay < 0)
>>  vblank_disable_fn(&vblank->disable_timer);
>> -else if (!dev->vblank_disable_immediate)
>> +else if (__vblank_disable_immediate(dev, pipe))
>>  mod_timer(&vblank->disable_timer,
>>jiffies + ((drm_vblank_offdelay * HZ)/1000));
>>  }
>> @@ -1663,7 +1659,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void 
>> *data,
>>  /* If the counter is currently enabled and accurate, short-circuit
>>   * queries to return the cached timestamp of the last vblank.
>>   */
>> -if (dev->vblank_disable_immediate &&
>> +if (__vblank_disable_immediate(dev, pipe) &&
>>  drm_wait_vblank_is_query(vblwait) &&
>>  READ_ONCE(vblank->enabled)) {
>>  drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
>> @@ -1820,7 +1816,7 @@ bool drm_handle_vblank(struct drm_device *dev, 
>> unsigned int pipe)
>>   * been signaled. The disable has to be last (after
>>   * drm_handle_vblank_events) so that the timestamp is always accurate.
>>   */
>> -disable_irq = (dev->vblank_disable_immediate &&
>> +disable_irq = (__vblank_disable_immediate(dev, pipe) &&
>> drm_vblank_offdelay > 0 &&
>> !atomic_read(&vblank->refcount));
>>  
>> @@ -1893,7 +1889,8 @@ int drm_crtc_get_sequence_ioctl(struct drm_device 
>> *dev, void *data,
>>  pipe = drm_crtc_index(crtc);
>>  
>>  vblank = &dev->vblank[pipe];
>> -vblank_enabled = dev->vblank_disable_immediate && 
>> READ_ONCE(vblank->enabled);
>> +vblank_enabled = __vblank_disable_immediate(dev, pipe) &&
>> + READ_ONCE(vblank->enabled);
>>  
>>  if (!vblank_enabled) {
>>  ret = drm_crtc_vblank_get(crtc);
>> -- 
>> 2.24.1
>>
>> ___
>> Intel-gfx mailing list
>> intel-...@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer



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Re: [Intel-gfx] [PATCH v2 02/21] drm: Evaluate struct drm_device.vblank_disable_immediate on each use

[Ville Syrjälä]

On Wed, Jan 15, 2020 at 01:16:33PM +0100, Thomas Zimmermann wrote:
> VBLANK interrupts can be disabled immediately or with a delay, where the
> latter is the default. The former option can be selected by setting
> get_vblank_timestamp, and enabling vblank_disable_immediate in struct
> drm_device.
> 
> The setup is only evaluated once when DRM initializes VBLANKs. Evaluating
> the settings on each use of vblank_disable_immediate will allow for easy
> integration of CRTC VBLANK functions.
> 
> Signed-off-by: Thomas Zimmermann 
> ---
>  drivers/gpu/drm/drm_vblank.c | 31 ++-
>  1 file changed, 14 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 3f1dd54cc8bb..abb085c67d82 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -481,19 +481,6 @@ int drm_vblank_init(struct drm_device *dev, unsigned int 
> num_crtcs)
>  
>   DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
>  
> - /* Driver specific high-precision vblank timestamping supported? */
> - if (dev->driver->get_vblank_timestamp)
> - DRM_INFO("Driver supports precise vblank timestamp query.\n");
> - else
> - DRM_INFO("No driver support for vblank timestamp query.\n");
> -
> - /* Must have precise timestamping for reliable vblank instant disable */
> - if (dev->vblank_disable_immediate && 
> !dev->driver->get_vblank_timestamp) {
> - dev->vblank_disable_immediate = false;
> - DRM_INFO("Setting vblank_disable_immediate to false because "
> -  "get_vblank_timestamp == NULL\n");
> - }

Which drivers are so broken they set vblank_disable_immediate to true
without having the vfunc specified? IMO this code should just go away
(or converted to a WARN).

> -
>   return 0;
>  
>  err:
> @@ -1070,6 +1057,15 @@ int drm_crtc_vblank_get(struct drm_crtc *crtc)
>  }
>  EXPORT_SYMBOL(drm_crtc_vblank_get);
>  
> +static bool __vblank_disable_immediate(struct drm_device *dev, unsigned int 
> pipe)
> +{
> + if (!dev->vblank_disable_immediate)
> + return false;
> + if (!dev->driver->get_vblank_timestamp)
> + return false;
> + return true;
> +}
> +
>  static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
>  {
>   struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
> @@ -1086,7 +1082,7 @@ static void drm_vblank_put(struct drm_device *dev, 
> unsigned int pipe)
>   return;
>   else if (drm_vblank_offdelay < 0)
>   vblank_disable_fn(&vblank->disable_timer);
> - else if (!dev->vblank_disable_immediate)
> + else if (__vblank_disable_immediate(dev, pipe))
>   mod_timer(&vblank->disable_timer,
> jiffies + ((drm_vblank_offdelay * HZ)/1000));
>   }
> @@ -1663,7 +1659,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void 
> *data,
>   /* If the counter is currently enabled and accurate, short-circuit
>* queries to return the cached timestamp of the last vblank.
>*/
> - if (dev->vblank_disable_immediate &&
> + if (__vblank_disable_immediate(dev, pipe) &&
>   drm_wait_vblank_is_query(vblwait) &&
>   READ_ONCE(vblank->enabled)) {
>   drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
> @@ -1820,7 +1816,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned 
> int pipe)
>* been signaled. The disable has to be last (after
>* drm_handle_vblank_events) so that the timestamp is always accurate.
>*/
> - disable_irq = (dev->vblank_disable_immediate &&
> + disable_irq = (__vblank_disable_immediate(dev, pipe) &&
>  drm_vblank_offdelay > 0 &&
>  !atomic_read(&vblank->refcount));
>  
> @@ -1893,7 +1889,8 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, 
> void *data,
>   pipe = drm_crtc_index(crtc);
>  
>   vblank = &dev->vblank[pipe];
> - vblank_enabled = dev->vblank_disable_immediate && 
> READ_ONCE(vblank->enabled);
> + vblank_enabled = __vblank_disable_immediate(dev, pipe) &&
> +  READ_ONCE(vblank->enabled);
>  
>   if (!vblank_enabled) {
>   ret = drm_crtc_vblank_get(crtc);
> -- 
> 2.24.1
> 
> ___
> Intel-gfx mailing list
> intel-...@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Ville Syrjälä
Intel
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[PATCH v2 02/21] drm: Evaluate struct drm_device.vblank_disable_immediate on each use

[Thomas Zimmermann]

VBLANK interrupts can be disabled immediately or with a delay, where the
latter is the default. The former option can be selected by setting
get_vblank_timestamp, and enabling vblank_disable_immediate in struct
drm_device.

The setup is only evaluated once when DRM initializes VBLANKs. Evaluating
the settings on each use of vblank_disable_immediate will allow for easy
integration of CRTC VBLANK functions.

Signed-off-by: Thomas Zimmermann 
---
 drivers/gpu/drm/drm_vblank.c | 31 ++-
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 3f1dd54cc8bb..abb085c67d82 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -481,19 +481,6 @@ int drm_vblank_init(struct drm_device *dev, unsigned int 
num_crtcs)
 
DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
 
-   /* Driver specific high-precision vblank timestamping supported? */
-   if (dev->driver->get_vblank_timestamp)
-   DRM_INFO("Driver supports precise vblank timestamp query.\n");
-   else
-   DRM_INFO("No driver support for vblank timestamp query.\n");
-
-   /* Must have precise timestamping for reliable vblank instant disable */
-   if (dev->vblank_disable_immediate && 
!dev->driver->get_vblank_timestamp) {
-   dev->vblank_disable_immediate = false;
-   DRM_INFO("Setting vblank_disable_immediate to false because "
-"get_vblank_timestamp == NULL\n");
-   }
-
return 0;
 
 err:
@@ -1070,6 +1057,15 @@ int drm_crtc_vblank_get(struct drm_crtc *crtc)
 }
 EXPORT_SYMBOL(drm_crtc_vblank_get);
 
+static bool __vblank_disable_immediate(struct drm_device *dev, unsigned int 
pipe)
+{
+   if (!dev->vblank_disable_immediate)
+   return false;
+   if (!dev->driver->get_vblank_timestamp)
+   return false;
+   return true;
+}
+
 static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
 {
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
@@ -1086,7 +1082,7 @@ static void drm_vblank_put(struct drm_device *dev, 
unsigned int pipe)
return;
else if (drm_vblank_offdelay < 0)
vblank_disable_fn(&vblank->disable_timer);
-   else if (!dev->vblank_disable_immediate)
+   else if (__vblank_disable_immediate(dev, pipe))
mod_timer(&vblank->disable_timer,
  jiffies + ((drm_vblank_offdelay * HZ)/1000));
}
@@ -1663,7 +1659,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void 
*data,
/* If the counter is currently enabled and accurate, short-circuit
 * queries to return the cached timestamp of the last vblank.
 */
-   if (dev->vblank_disable_immediate &&
+   if (__vblank_disable_immediate(dev, pipe) &&
drm_wait_vblank_is_query(vblwait) &&
READ_ONCE(vblank->enabled)) {
drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
@@ -1820,7 +1816,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned 
int pipe)
 * been signaled. The disable has to be last (after
 * drm_handle_vblank_events) so that the timestamp is always accurate.
 */
-   disable_irq = (dev->vblank_disable_immediate &&
+   disable_irq = (__vblank_disable_immediate(dev, pipe) &&
   drm_vblank_offdelay > 0 &&
   !atomic_read(&vblank->refcount));
 
@@ -1893,7 +1889,8 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, 
void *data,
pipe = drm_crtc_index(crtc);
 
vblank = &dev->vblank[pipe];
-   vblank_enabled = dev->vblank_disable_immediate && 
READ_ONCE(vblank->enabled);
+   vblank_enabled = __vblank_disable_immediate(dev, pipe) &&
+READ_ONCE(vblank->enabled);
 
if (!vblank_enabled) {
ret = drm_crtc_vblank_get(crtc);
-- 
2.24.1

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