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drm/vblank: Allow dynamic per-crtc max_vblank_count

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[ Upstream commit ed20151a7699bb2c77eba3610199789a126940c4 ]

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)

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>
Link: https://patchwork.freedesktop.org/patch/msgid/20181127182004.28885-1-ville.syrjala@linux.intel.com
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Ville Syrjälä 2018-11-27 20:20:04 +02:00 committed by Greg Kroah-Hartman
parent 71f7191054
commit 2b4f567912
3 changed files with 71 additions and 4 deletions
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45
drivers/gpu/drm/drm_vblank.c
View file

@ -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

8
include/drm/drm_device.h
View file

@ -174,7 +174,13 @@ 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 */

22
include/drm/drm_vblank.h
View file

@ -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