drm/radeon: handle broken disabled rb mask gracefully (6xx/7xx) (v2)

This is a port of cedb655a3a7764c3fd946077944383c9e0e68dd4
to older asics.  Fixes a possible divide by 0 if the harvest
register is invalid.

v2: drop some additional harvest munging.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

2 files changed, 16 insertions, 33 deletions

diff --git a/drivers/gpu/drm/radeon/r600.c b/drivers/gpu/drm/radeon/r600.c
index e8bf0ea2dade..e616eb5f6e7a 100644
--- a/drivers/gpu/drm/radeon/r600.c
+++ b/drivers/gpu/drm/radeon/r600.c
@@ -1812,7 +1812,6 @@ static void r600_gpu_init(struct radeon_device *rdev)
 {
         u32 tiling_config;
         u32 ramcfg;
-        u32 cc_rb_backend_disable;
         u32 cc_gc_shader_pipe_config;
         u32 tmp;
         int i, j;
@@ -1939,29 +1938,20 @@ static void r600_gpu_init(struct radeon_device *rdev)
         }
         tiling_config |= BANK_SWAPS(1);
 
-        cc_rb_backend_disable = RREG32(CC_RB_BACKEND_DISABLE) & 0x00ff0000;
-        tmp = R6XX_MAX_BACKENDS -
-                r600_count_pipe_bits((cc_rb_backend_disable >> 16) & R6XX_MAX_BACKENDS_MASK);
-        if (tmp < rdev->config.r600.max_backends) {
-                rdev->config.r600.max_backends = tmp;
-        }
-
         cc_gc_shader_pipe_config = RREG32(CC_GC_SHADER_PIPE_CONFIG) & 0x00ffff00;
-        tmp = R6XX_MAX_PIPES -
-                r600_count_pipe_bits((cc_gc_shader_pipe_config >> 8) & R6XX_MAX_PIPES_MASK);
-        if (tmp < rdev->config.r600.max_pipes) {
-                rdev->config.r600.max_pipes = tmp;
-        }
-        tmp = R6XX_MAX_SIMDS -
-                r600_count_pipe_bits((cc_gc_shader_pipe_config >> 16) & R6XX_MAX_SIMDS_MASK);
-        if (tmp < rdev->config.r600.max_simds) {
-                rdev->config.r600.max_simds = tmp;
-        }
         tmp = rdev->config.r600.max_simds -
                 r600_count_pipe_bits((cc_gc_shader_pipe_config >> 16) & R6XX_MAX_SIMDS_MASK);
         rdev->config.r600.active_simds = tmp;
 
         disabled_rb_mask = (RREG32(CC_RB_BACKEND_DISABLE) >> 16) & R6XX_MAX_BACKENDS_MASK;
+        tmp = 0;
+        for (i = 0; i < rdev->config.r600.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.r600.max_backends; i++)
+                        disabled_rb_mask &= ~(1 << i);
+        }
         tmp = (tiling_config & PIPE_TILING__MASK) >> PIPE_TILING__SHIFT;
         tmp = r6xx_remap_render_backend(rdev, tmp, rdev->config.r600.max_backends,
                                         R6XX_MAX_BACKENDS, disabled_rb_mask);
diff --git a/drivers/gpu/drm/radeon/rv770.c b/drivers/gpu/drm/radeon/rv770.c
index 2983f17ea1b3..d9f5ce715c9b 100644
--- a/drivers/gpu/drm/radeon/rv770.c
+++ b/drivers/gpu/drm/radeon/rv770.c
@@ -1177,7 +1177,6 @@ static void rv770_gpu_init(struct radeon_device *rdev)
         u32 hdp_host_path_cntl;
         u32 sq_dyn_gpr_size_simd_ab_0;
         u32 gb_tiling_config = 0;
-        u32 cc_rb_backend_disable = 0;
         u32 cc_gc_shader_pipe_config = 0;
         u32 mc_arb_ramcfg;
         u32 db_debug4, tmp;
@@ -1311,21 +1310,7 @@ static void rv770_gpu_init(struct radeon_device *rdev)
                 WREG32(SPI_CONFIG_CNTL, 0);
         }
 
-        cc_rb_backend_disable = RREG32(CC_RB_BACKEND_DISABLE) & 0x00ff0000;
-        tmp = R7XX_MAX_BACKENDS - r600_count_pipe_bits(cc_rb_backend_disable >> 16);
-        if (tmp < rdev->config.rv770.max_backends) {
-                rdev->config.rv770.max_backends = tmp;
-        }
-
         cc_gc_shader_pipe_config = RREG32(CC_GC_SHADER_PIPE_CONFIG) & 0xffffff00;
-        tmp = R7XX_MAX_PIPES - r600_count_pipe_bits((cc_gc_shader_pipe_config >> 8) & R7XX_MAX_PIPES_MASK);
-        if (tmp < rdev->config.rv770.max_pipes) {
-                rdev->config.rv770.max_pipes = tmp;
-        }
-        tmp = R7XX_MAX_SIMDS - r600_count_pipe_bits((cc_gc_shader_pipe_config >> 16) & R7XX_MAX_SIMDS_MASK);
-        if (tmp < rdev->config.rv770.max_simds) {
-                rdev->config.rv770.max_simds = tmp;
-        }
         tmp = rdev->config.rv770.max_simds -
                 r600_count_pipe_bits((cc_gc_shader_pipe_config >> 16) & R7XX_MAX_SIMDS_MASK);
         rdev->config.rv770.active_simds = tmp;
@@ -1348,6 +1333,14 @@ static void rv770_gpu_init(struct radeon_device *rdev)
         rdev->config.rv770.tiling_npipes = rdev->config.rv770.max_tile_pipes;
 
         disabled_rb_mask = (RREG32(CC_RB_BACKEND_DISABLE) >> 16) & R7XX_MAX_BACKENDS_MASK;
+        tmp = 0;
+        for (i = 0; i < rdev->config.rv770.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.rv770.max_backends; i++)
+                        disabled_rb_mask &= ~(1 << i);
+        }
         tmp = (gb_tiling_config & PIPE_TILING__MASK) >> PIPE_TILING__SHIFT;
         tmp = r6xx_remap_render_backend(rdev, tmp, rdev->config.rv770.max_backends,
                                         R7XX_MAX_BACKENDS, disabled_rb_mask);