Re: [PATCH 04/12] drm: Add drm_vblank_on()

Daniel Vetter
2014-05-14T18:55:16Z

On Wed, May 14, 2014 at 08:51:06PM +0200, Daniel Vetter wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> drm_vblank_off() will turn off vblank interrupts, but as long as the
> refcount is elevated drm_vblank_get() will not re-enable them. This
> is a problem is someone is holding a vblank reference while a modeset is
> happening, and the driver requires vblank interrupt to work during that
> time.
>
> Add drm_vblank_on() as a counterpart to drm_vblank_off() which will
> re-enabled vblank interrupts if the refcount is already elevated. This
> will allow drivers to choose the specific places in the modeset sequence
> at which vblank interrupts get disabled and enabled.
>
> Testcase: igt/kms_flip/*-vs-suspend

Testcase: igt/kms_flip/*-vs-vblank-race

> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> [danvet: Add Testcase tag for the igt I've written.]
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
> drivers/gpu/drm/drm_irq.c | 72 ++++++++++++++++++++++++++----------
> drivers/gpu/drm/i915/intel_display.c | 8 ++++
> include/drm/drmP.h | 1 +
> 3 files changed, 62 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 13d671ed3421..dd786d84daab 100644
> --- a/drivers/gpu/drm/drm_irq.c
> +++ b/drivers/gpu/drm/drm_irq.c
> @@ -840,6 +840,41 @@ static void drm_update_vblank_count(struct drm_device *dev, int crtc)
> }
>
> /**
> + * drm_vblank_enable - enable the vblank interrupt on a CRTC
> + * @dev: DRM device
> + * @crtc: CRTC in question
> + */
> +static int drm_vblank_enable(struct drm_device *dev, int crtc)
> +{
> + int ret = 0;
> +
> + assert_spin_locked(&dev->vbl_lock);
> +
> + spin_lock(&dev->vblank_time_lock);
> +
> + if (!dev->vblank[crtc].enabled) {
> + /* Enable vblank irqs under vblank_time_lock protection.
> + * All vblank count & timestamp updates are held off
> + * until we are done reinitializing master counter and
> + * timestamps. Filtercode in drm_handle_vblank() will
> + * prevent double-accounting of same vblank interval.
> + */
> + ret = dev->driver->enable_vblank(dev, crtc);
> + DRM_DEBUG("enabling vblank on crtc %d, ret: %d\n", crtc, ret);
> + if (ret)
> + atomic_dec(&dev->vblank[crtc].refcount);
> + else {
> + dev->vblank[crtc].enabled = true;
> + drm_update_vblank_count(dev, crtc);
> + }
> + }
> +
> + spin_unlock(&dev->vblank_time_lock);
> +
> + return ret;
> +}
> +
> +/**
> * drm_vblank_get - get a reference count on vblank events
> * @dev: DRM device
> * @crtc: which CRTC to own
> @@ -858,25 +893,7 @@ int drm_vblank_get(struct drm_device *dev, int crtc)
> spin_lock_irqsave(&dev->vbl_lock, irqflags);
> /* Going from 0->1 means we have to enable interrupts again */
> if (atomic_add_return(1, &dev->vblank[crtc].refcount) == 1) {
> - spin_lock(&dev->vblank_time_lock);
> - if (!dev->vblank[crtc].enabled) {
> - /* Enable vblank irqs under vblank_time_lock protection.
> - * All vblank count & timestamp updates are held off
> - * until we are done reinitializing master counter and
> - * timestamps. Filtercode in drm_handle_vblank() will
> - * prevent double-accounting of same vblank interval.
> - */
> - ret = dev->driver->enable_vblank(dev, crtc);
> - DRM_DEBUG("enabling vblank on crtc %d, ret: %d\n",
> - crtc, ret);
> - if (ret)
> - atomic_dec(&dev->vblank[crtc].refcount);
> - else {
> - dev->vblank[crtc].enabled = true;
> - drm_update_vblank_count(dev, crtc);
> - }
> - }
> - spin_unlock(&dev->vblank_time_lock);
> + ret = drm_vblank_enable(dev, crtc);
> } else {
> if (!dev->vblank[crtc].enabled) {
> atomic_dec(&dev->vblank[crtc].refcount);
> @@ -946,6 +963,23 @@ void drm_vblank_off(struct drm_device *dev, int crtc)
> EXPORT_SYMBOL(drm_vblank_off);
>
> /**
> + * drm_vblank_on - enable vblank events on a CRTC
> + * @dev: DRM device
> + * @crtc: CRTC in question
> + */
> +void drm_vblank_on(struct drm_device *dev, int crtc)
> +{
> + unsigned long irqflags;
> +
> + spin_lock_irqsave(&dev->vbl_lock, irqflags);
> + /* re-enable interrupts if there's are users left */
> + if (atomic_read(&dev->vblank[crtc].refcount) != 0)
> + WARN_ON(drm_vblank_enable(dev, crtc));
> + spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
> +}
> +EXPORT_SYMBOL(drm_vblank_on);
> +
> +/**
> * drm_vblank_pre_modeset - account for vblanks across mode sets
> * @dev: DRM device
> * @crtc: CRTC in question
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b39d0367dd68..858c393b051f 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -3739,6 +3739,8 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
> * happening.
> */
> intel_wait_for_vblank(dev, intel_crtc->pipe);
> +
> + drm_vblank_on(dev, pipe);
> }
>
> /* IPS only exists on ULT machines and is tied to pipe A. */
> @@ -3830,6 +3832,8 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
> * to change the workaround. */
> haswell_mode_set_planes_workaround(intel_crtc);
> ilk_crtc_enable_planes(crtc);
> +
> + drm_vblank_on(dev, pipe);
> }
>
> static void ironlake_pfit_disable(struct intel_crtc *crtc)
> @@ -4353,6 +4357,8 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
>
> for_each_encoder_on_crtc(dev, crtc, encoder)
> encoder->enable(encoder);
> +
> + drm_vblank_on(dev, pipe);
> }
>
> static void i9xx_crtc_enable(struct drm_crtc *crtc)
> @@ -4400,6 +4406,8 @@ static void i9xx_crtc_enable(struct drm_crtc *crtc)
>
> for_each_encoder_on_crtc(dev, crtc, encoder)
> encoder->enable(encoder);
> +
> + drm_vblank_on(dev, pipe);
> }
>
> static void i9xx_pfit_disable(struct intel_crtc *crtc)
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 9d982d483f12..7339b2b00724 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -1360,6 +1360,7 @@ extern bool drm_handle_vblank(struct drm_device *dev, int crtc);
> extern int drm_vblank_get(struct drm_device *dev, int crtc);
> extern void drm_vblank_put(struct drm_device *dev, int crtc);
> extern void drm_vblank_off(struct drm_device *dev, int crtc);
> +extern void drm_vblank_on(struct drm_device *dev, int crtc);
> extern void drm_vblank_cleanup(struct drm_device *dev);
> extern u32 drm_get_last_vbltimestamp(struct drm_device *dev, int crtc,
> struct timeval *tvblank, unsigned flags);
> --
> 1.8.3.1
>

--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch