drm/i915: Set the Stencil Cache eviction policy to non-LRA mode.

commit 3a69ddd6f872180b6f61fda87152b37202118fbc upstream.

Clearing bit 5 of CACHE_MODE_0 is necessary to prevent GPU hangs in
OpenGL programs such as Google MapsGL, Google Earth, and gzdoom when
using separate stencil buffers.  Without it, the GPU tries to use the
LRA eviction policy, which isn't supported.  This was supposed to be off
by default, but seems to be on for many machines.

This cannot be done in gen6_init_clock_gating with most of the other
workaround bits; the render ring needs to exist.  Otherwise, the
register write gets dropped on the floor (one printk will show it
changed, but a second printk immediately following shows the value
reverts to the old one).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47535
Cc: Rob Castle <futuredub@gmail.com>
Cc: Eric Appleman <erappleman@gmail.com>
Cc: aaron667@gmx.net
Cc: Keith Packard <keithp@keithp.com>
Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 3e6429a4dbe732b612951cec8ebd83a4ea33e0af..ac38d211352175845c5303d02256a70d9cb20385 100644 (file)
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -523,6 +523,7 @@
 #define   CM0_MASK_SHIFT          16
 #define   CM0_IZ_OPT_DISABLE      (1<<6)
 #define   CM0_ZR_OPT_DISABLE      (1<<5)
+#define          CM0_STC_EVICT_DISABLE_LRA_SNB (1<<5)
 #define   CM0_DEPTH_EVICT_DISABLE (1<<4)
 #define   CM0_COLOR_EVICT_DISABLE (1<<3)
 #define   CM0_DEPTH_WRITE_DISABLE (1<<1)

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index cbc3c049611ecb6cd6978f3deebf54616912ee36..99f71aff174b61318f0dcf5fe8816a884618ab39 100644 (file)
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -417,6 +417,14 @@ static int init_render_ring(struct intel_ring_buffer *ring)
        if (INTEL_INFO(dev)->gen >= 6) {
                I915_WRITE(INSTPM,
                           INSTPM_FORCE_ORDERING << 16 | INSTPM_FORCE_ORDERING);
+
+               /* From the Sandybridge PRM, volume 1 part 3, page 24:
+                * "If this bit is set, STCunit will have LRA as replacement
+                *  policy. [...] This bit must be reset.  LRA replacement
+                *  policy is not supported."
+                */
+               I915_WRITE(CACHE_MODE_0,
+                          CM0_STC_EVICT_DISABLE_LRA_SNB << CM0_MASK_SHIFT);
        }
 
        return ret;