If we disable the pipe and the GPU is currently waiting on a scanline WAIT_FOR_EVENT, the GPU will hang. Fortunately, there is a magic bit which we can write on i915+ to break this wait after disabling the pipe.
References: Bug 29252 - [Arrandale] Hung WAIT_FOR_EVENT when running rss-glx-skyrocket https://bugs.freedesktop.org/show_bug.cgi?id=29252 Bug 28964 - [i965gm] GPU infinite MI_WAIT_FOR_EVENT while watching video in Totem https://bugs.freedesktop.org/show_bug.cgi?id=28964 and many others. Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk> Cc: Jesse Barnes <jbar...@virtuousgeek.org> --- drivers/gpu/drm/i915/i915_reg.h | 2 ++ drivers/gpu/drm/i915/intel_display.c | 31 +++++++++++++++++++++++++++++-- 2 files changed, 31 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index 67e3ec1..9dedf36 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -295,6 +295,8 @@ #define RING_VALID_MASK 0x00000001 #define RING_VALID 0x00000001 #define RING_INVALID 0x00000000 +#define RING_WAIT_I8XX (1<<0) /* gen2, PRBx_HEAD */ +#define RING_WAIT (1<<11) /* gen3+, PRBx_CTL */ #define PRB1_TAIL 0x02040 /* 915+ only */ #define PRB1_HEAD 0x02044 /* 915+ only */ #define PRB1_START 0x02048 /* 915+ only */ diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index e57596a..b9c6487 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -2412,6 +2412,26 @@ static void i9xx_crtc_dpms(struct drm_crtc *crtc, int mode) } } +/* + * When we disable a pipe, we need to clear any pending scanline wait events + * to avoid hanging the ring, which we assume we are waiting on. + */ +static void intel_clear_scanline_wait(struct drm_device *dev) +{ + struct drm_i915_private *dev_priv = dev->dev_private; + u32 tmp; + + if (IS_GEN2(dev)) + /* Can't break the hang on i8xx */ + return; + + tmp = I915_READ(PRB0_CTL); + if (tmp & RING_WAIT) { + I915_WRITE(PRB0_CTL, tmp); + POSTING_READ(PRB0_CTL); + } +} + /** * Sets the power management mode of the pipe and plane. */ @@ -2431,7 +2451,8 @@ static void intel_crtc_dpms(struct drm_crtc *crtc, int mode) * with multiple pipes prior to enabling to new pipe. * * When switching off the display, make sure the cursor is - * properly hidden prior to disabling the pipe. + * properly hidden and there are no pending waits prior to + * disabling the pipe. */ if (mode == DRM_MODE_DPMS_ON) intel_update_watermarks(dev); @@ -2442,8 +2463,14 @@ static void intel_crtc_dpms(struct drm_crtc *crtc, int mode) if (mode == DRM_MODE_DPMS_ON) intel_crtc_update_cursor(crtc); - else + else { + /* XXX Note that this is not a complete solution, but a hack + * to avoid the most frequently hit hang. + */ + intel_clear_scanline_wait(dev); + intel_update_watermarks(dev); + } if (!dev->primary->master) return; -- 1.7.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx
