drm/radeon: handle broken disabled rb mask gracefully

If the disabled rb mask register is not properly initialized
program a sane default based on the number of RBs for the
asic.  This avoids a potential divide by 0 when calculating
the backend mask.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

2 files changed, 16 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index cd7951060afd..b114252e7810 100644
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -2261,6 +2261,14 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
         }
         /* enabled rb are just the one not disabled :) */
         disabled_rb_mask = tmp;
+        tmp = 0;
+        for (i = 0; i < rdev->config.evergreen.max_backends; i++)
+                tmp |= (1 << i);
+        /* if all the backends are disabled, fix it up here */
+        if ((disabled_rb_mask & tmp) == tmp) {
+                for (i = 0; i < rdev->config.evergreen.max_backends; i++)
+                        disabled_rb_mask &= ~(1 << i);
+        }
 
         WREG32(GRBM_GFX_INDEX, INSTANCE_BROADCAST_WRITES | SE_BROADCAST_WRITES);
         WREG32(RLC_GFX_INDEX, INSTANCE_BROADCAST_WRITES | SE_BROADCAST_WRITES);
diff --git a/drivers/gpu/drm/radeon/ni.c b/drivers/gpu/drm/radeon/ni.c
index a23503e16083..78aead0ada7b 100644
--- a/drivers/gpu/drm/radeon/ni.c
+++ b/drivers/gpu/drm/radeon/ni.c
@@ -615,6 +615,14 @@ static void cayman_gpu_init(struct radeon_device *rdev)
         }
         /* enabled rb are just the one not disabled :) */
         disabled_rb_mask = tmp;
+        tmp = 0;
+        for (i = 0; i < (rdev->config.cayman.max_backends_per_se * rdev->config.cayman.max_shader_engines); i++)
+                tmp |= (1 << i);
+        /* if all the backends are disabled, fix it up here */
+        if ((disabled_rb_mask & tmp) == tmp) {
+                for (i = 0; i < (rdev->config.cayman.max_backends_per_se * rdev->config.cayman.max_shader_engines); i++)
+                        disabled_rb_mask &= ~(1 << i);
+        }
 
         WREG32(GRBM_GFX_INDEX, INSTANCE_BROADCAST_WRITES | SE_BROADCAST_WRITES);
         WREG32(RLC_GFX_INDEX, INSTANCE_BROADCAST_WRITES | SE_BROADCAST_WRITES);