Re: [PATCH v2 01/15] drm/vblank: Allow dynamic per-crtc max_vblank_count

On Tue, Nov 27, 2018 at 08:20:04PM +0200, Ville Syrjala wrote:

From: Ville Syrjälä ville.syrjala@linux.intel.com

On i965gm we need to adjust max_vblank_count dynamically depending on whether the TV encoder is used or not. To that end add a per-crtc max_vblank_count that takes precedence over its device wide counterpart. The driver can now call drm_crtc_set_max_vblank_count() to configure the per-crtc value before calling drm_vblank_on().

Also looks like there was some discussion about exynos needing similar treatment.

v2: Drop the extra max_vblank_count!=0 check for the WARN(last!=current), will take care of it in i915 code (Daniel) WARN_ON(!inmodeset) (Daniel) WARN_ON(dev->max_vblank_count) Pimp up the docs (Daniel)

Yeah I'm happy with the pile of WARN_ON here. And docs look great too.

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

Cc: stable@vger.kernel.org Cc: Inki Dae inki.dae@samsung.com Cc: Daniel Vetter daniel@ffwll.ch Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com

---

drivers/gpu/drm/drm_vblank.c | 45 +++++++++++++++++++++++++++++++++--- include/drm/drm_device.h | 8 ++++++- include/drm/drm_vblank.h | 22 ++++++++++++++++++ 3 files changed, 71 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 98e091175921..cde71ee95a8f 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -105,13 +105,20 @@ static void store_vblank(struct drm_device *dev, unsigned int pipe, write_sequnlock(&vblank->seqlock); } +static u32 drm_max_vblank_count(struct drm_device *dev, unsigned int pipe) +{

• struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
• return vblank->max_vblank_count ?: dev->max_vblank_count;

+}

/*

• "No hw counter" fallback implementation of .get_vblank_counter() hook,
• if there is no useable hardware frame counter available.

*/ static u32 drm_vblank_no_hw_counter(struct drm_device *dev, unsigned int pipe) {

• WARN_ON_ONCE(dev->max_vblank_count != 0);

• WARN_ON_ONCE(drm_max_vblank_count(dev, pipe) != 0); return 0;

} @@ -198,6 +205,7 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, ktime_t t_vblank; int count = DRM_TIMESTAMP_MAXRETRIES; int framedur_ns = vblank->framedur_ns;

• u32 max_vblank_count = drm_max_vblank_count(dev, pipe);

/* * Interrupts were disabled prior to this call, so deal with counter @@ -216,9 +224,9 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe, rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, in_vblank_irq); } while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);

• if (dev->max_vblank_count != 0) {

• if (max_vblank_count) { /* trust the hw counter when it's around */

• diff = (cur_vblank - vblank->last) & dev->max_vblank_count;
  

• diff = (cur_vblank - vblank->last) & max_vblank_count;
  

  } else if (rc && framedur_ns) { u64 diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));

@@ -1204,6 +1212,37 @@ void drm_crtc_vblank_reset(struct drm_crtc *crtc) } EXPORT_SYMBOL(drm_crtc_vblank_reset); +/**

• • drm_crtc_set_max_vblank_count - configure the hw max vblank counter value
• • @crtc: CRTC in question
• • @max_vblank_count: max hardware vblank counter value
• • Update the maximum hardware vblank counter value for @crtc
• • at runtime. Useful for hardware where the operation of the
• • hardware vblank counter depends on the currently active
• • display configuration.
• • For example, if the hardware vblank counter does not work
• • when a specific connector is active the maximum can be set
• • to zero. And when that specific connector isn't active the
• • maximum can again be set to the appropriate non-zero value.
• • If used, must be called before drm_vblank_on().
• */

+void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,

• 		   u32 max_vblank_count)
  

+{

• struct drm_device *dev = crtc->dev;
• unsigned int pipe = drm_crtc_index(crtc);
• struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
• WARN_ON(dev->max_vblank_count);
• WARN_ON(!READ_ONCE(vblank->inmodeset));
• vblank->max_vblank_count = max_vblank_count;

+} +EXPORT_SYMBOL(drm_crtc_set_max_vblank_count);

/**

• drm_crtc_vblank_on - enable vblank events on a CRTC
• @crtc: CRTC in question

diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h index 42411b3ea0c8..45e43ce9652f 100644 --- a/include/drm/drm_device.h +++ b/include/drm/drm_device.h @@ -184,7 +184,13 @@ struct drm_device { * races and imprecision over longer time periods, hence exposing a * hardware vblank counter is always recommended. *

• * If non-zeor, &drm_crtc_funcs.get_vblank_counter must be set.
  

• * This is the statically configured device wide maximum. The driver
  

• * can instead choose to use a runtime configurable per-crtc value
  

• * &drm_vblank_crtc.max_vblank_count, in which case @max_vblank_count
  

• * must be left at zero. See drm_crtc_set_max_vblank_count() on how
  

• * to use the per-crtc value.
  

• *
  

• * If non-zero, &drm_crtc_funcs.get_vblank_counter must be set.
  

  */ u32 max_vblank_count; /**< size of vblank counter register */

diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index 6ad9630d4f48..e528bb2f659d 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -128,6 +128,26 @@ struct drm_vblank_crtc { * @last: Protected by &drm_device.vbl_lock, used for wraparound handling. */ u32 last;

• /**

• * @max_vblank_count:
  

• *
  

• * Maximum value of the vblank registers for this crtc. This value +1
  

• * will result in a wrap-around of the vblank register. It is used
  

• * by the vblank core to handle wrap-arounds.
  

• *
  

• * If set to zero the vblank core will try to guess the elapsed vblanks
  

• * between times when the vblank interrupt is disabled through
  

• * high-precision timestamps. That approach is suffering from small
  

• * races and imprecision over longer time periods, hence exposing a
  

• * hardware vblank counter is always recommended.
  

• *
  

• * This is the runtime configurable per-crtc maximum set through
  

• * drm_crtc_set_max_vblank_count(). If this is used the driver
  

• * must leave the device wide &drm_device.max_vblank_count at zero.
  

• *
  

• * If non-zero, &drm_crtc_funcs.get_vblank_counter must be set.
  

• */
  

• u32 max_vblank_count; /**
  • @inmodeset: Tracks whether the vblank is disabled due to a modeset.
  • For legacy driver bit 2 additionally tracks whether an additional

@@ -206,4 +226,6 @@ bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, void drm_calc_timestamping_constants(struct drm_crtc *crtc, const struct drm_display_mode *mode); wait_queue_head_t *drm_crtc_vblank_waitqueue(struct drm_crtc *crtc); +void drm_crtc_set_max_vblank_count(struct drm_crtc *crtc,

• 		   u32 max_vblank_count);
  

#endif

2.18.1