drm/i915: Restore rps/rc6 on reset

A check of rps/rc6 state after i915_reset determined that the ring
MAX_IDLE registers were returned to their hardware defaults and that
the GEN6_PMIMR register was set to mask all interrupts. This change
restores those values to their pre-reset states by re-initializing
rps/rc6 in i915_reset. A full re-initialization was opted for versus
a targeted set of restore operations for simplicity and maintain-
ability. Note that the re-initialization is not done for Ironlake,
due to a past comment that it causes problems.

Also updated the rps initialization sequence to preserve existing
min/max values in the case of a re-init. We assume the values were
validated upon being set and do not do further range checking. The
debugfs interface for changing min/max was updated with range
checking to ensure this condition (already present in sysfs
interface).

v2: fix rps logging to output hw_max and hw_min, not rps.max_delay
    and rps.min_delay which don't strictly represent hardware limits.
    Add igt testcase to signed-off-by section.

Testcase: igt/pm_rps/reset
Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 05072cf5a00..2d05d7ce4c2 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -728,6 +728,17 @@ int i915_reset(struct drm_device *dev)
 
 		drm_irq_uninstall(dev);
 		drm_irq_install(dev);
+
+		/* rps/rc6 re-init is necessary to restore state lost after the
+		 * reset and the re-install of drm irq. Skip for ironlake per
+		 * previous concerns that it doesn't respond well to some forms
+		 * of re-init after reset. */
+		if (INTEL_INFO(dev)->gen > 5) {
+			mutex_lock(&dev->struct_mutex);
+			intel_enable_gt_powersave(dev);
+			mutex_unlock(&dev->struct_mutex);
+		}
+
 		intel_hpd_init(dev);
 	} else {
 		mutex_unlock(&dev->struct_mutex);