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[0644/1094] drm/i915: fix infinite loop at gen6_update_ring_freq

Message ID 1413889294-31328-645-git-send-email-dheerajx.s.jamwal@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Dheeraj Jamwal Oct. 21, 2014, 10:54 a.m. UTC 
From: Paulo Zanoni <paulo.r.zanoni@intel.com>

If I boot my Broadwell machine to X on a system with Mesa Gallium
llvmpipe instead of i965, then kill X and try to run pm_pc8.c, when we
disable PC8 and call gen6_update_ring_freq(), we will get stuck on an
infinite loop because the frequencies are zero and the variables are
unsigned. This happens because we never ran any batch, so we did not
enable RC6, so the variables are zero. If I run gem_exec_nop before
running pm_pc8, everything works as expected because gem_exec_nop
makes RC6 be enabled.

This commit should prevent the infinite loop, which IMHO is already a
good reason to be merged, but it is not the proper fix to the "RC6 is
not being enabled" problem.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
(cherry picked from commit 4b28a1f3ef55a3b0b68dbab1fe6dbaf18e186710)

Signed-off-by: Dheeraj Jamwal <dheerajx.s.jamwal@intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 52ddca0..540fec2 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3537,7 +3537,8 @@  void gen6_update_ring_freq(struct drm_device *dev)
 	 * to use for memory access.  We do this by specifying the IA frequency
 	 * the PCU should use as a reference to determine the ring frequency.
 	 */
-	for (gpu_freq = dev_priv->rps.max_freq_softlimit; gpu_freq >= dev_priv->rps.min_freq_softlimit;
+	for (gpu_freq = dev_priv->rps.max_freq_softlimit;
+	     gpu_freq >= dev_priv->rps.min_freq_softlimit && gpu_freq != 0;
 	     gpu_freq--) {
 		int diff = dev_priv->rps.max_freq_softlimit - gpu_freq;
 		unsigned int ia_freq = 0, ring_freq = 0;