If we try to do that and the scanlines just wouldn't advance, we busy-hang the machine holding the modeset mutex. Not great for debugging. References: https://bugzilla.kernel.org/show_bug.cgi?id=43020 Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> --- drivers/gpu/drm/i915/intel_crt.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_crt.c b/drivers/gpu/drm/i915/intel_crt.c index 0976137..d30779e 100644 --- a/drivers/gpu/drm/i915/intel_crt.c +++ b/drivers/gpu/drm/i915/intel_crt.c @@ -383,6 +383,7 @@ intel_crt_load_detect(struct intel_crt *crt) } else { bool restore_vblank = false; int count, detect; + unsigned long timeout; /* * If there isn't any border, add some. @@ -407,22 +408,32 @@ intel_crt_load_detect(struct intel_crt *crt) /* * Wait for the border to be displayed */ - while (I915_READ(pipe_dsl_reg) >= vactive) - ; - while ((dsl = I915_READ(pipe_dsl_reg)) <= vsample) - ; + if (wait_for(I915_READ(pipe_dsl_reg) >= vactive, 1000)) + DRM_ERROR("timed out waiting for vactive in " + "load_detect, scanline: %u\n", + I915_READ(pipe_dsl_reg)); + if (wait_for((dsl = I915_READ(pipe_dsl_reg)) <= vsample, 1000)) + DRM_ERROR("timed out waiting for vsample in " + "load_detect, scanline: %u\n", + I915_READ(pipe_dsl_reg)); /* * Watch ST00 for an entire scanline */ detect = 0; count = 0; + timeout = jiffies + msecs_to_jiffies(1000); do { count++; /* Read the ST00 VGA status register */ st00 = I915_READ8(VGA_MSR_WRITE); if (st00 & (1 << 4)) detect++; - } while ((I915_READ(pipe_dsl_reg) == dsl)); + } while ((I915_READ(pipe_dsl_reg) == dsl) && + !time_after(jiffies, timeout)); + + if (time_after(jiffies, timeout)) + DRM_ERROR("timed out while load-detecting, scanline: %u\n", + I915_READ(pipe_dsl_reg)); /* restore vblank if necessary */ if (restore_vblank) -- 1.7.10
