drm/radeon: Use direct mapping for fast fb access on RS690

This patch allows the CPU to map the stolen vram segment
directly rather than going through the PCI BAR.  This
significantly improves performance for certain workloads with
a properly patched ddx.

Use radeon.fastfb=1 to enable it (disabled by default).
Currently only supported on RS690, but support for RS780/880
and newer APUs may be added eventually.

Signed-off-by: Samuel Li <samuel.li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/rs690.c b/drivers/gpu/drm/radeon/rs690.c
index 5706d2ac75ab..ab4c86cfd552 100644
--- a/drivers/gpu/drm/radeon/rs690.c
+++ b/drivers/gpu/drm/radeon/rs690.c
@@ -148,6 +148,8 @@ void rs690_pm_info(struct radeon_device *rdev)
 static void rs690_mc_init(struct radeon_device *rdev)
 {
         u64 base;
+        uint32_t h_addr, l_addr;
+        unsigned long long k8_addr;
 
         rs400_gart_adjust_size(rdev);
         rdev->mc.vram_is_ddr = true;
@@ -160,6 +162,27 @@ static void rs690_mc_init(struct radeon_device *rdev)
         base = RREG32_MC(R_000100_MCCFG_FB_LOCATION);
         base = G_000100_MC_FB_START(base) << 16;
         rdev->mc.igp_sideport_enabled = radeon_atombios_sideport_present(rdev);
+
+        /* Use K8 direct mapping for fast fb access. */ 
+        rdev->fastfb_working = false;
+        h_addr = G_00005F_K8_ADDR_EXT(RREG32_MC(R_00005F_MC_MISC_UMA_CNTL));
+        l_addr = RREG32_MC(R_00001E_K8_FB_LOCATION);
+        k8_addr = ((unsigned long long)h_addr) << 32 | l_addr;
+#if defined(CONFIG_X86_32) && !defined(CONFIG_X86_PAE)
+        if (k8_addr + rdev->mc.visible_vram_size < 0x100000000ULL)      
+#endif
+        {
+                /* FastFB shall be used with UMA memory. Here it is simply disabled when sideport 
+                 * memory is present.
+                 */
+                if (rdev->mc.igp_sideport_enabled == false && radeon_fastfb == 1) {
+                        DRM_INFO("Direct mapping: aper base at 0x%llx, replaced by direct mapping base 0x%llx.\n", 
+                                        (unsigned long long)rdev->mc.aper_base, k8_addr);
+                        rdev->mc.aper_base = (resource_size_t)k8_addr;
+                        rdev->fastfb_working = true;
+                }
+        }  
+
         rs690_pm_info(rdev);
         radeon_vram_location(rdev, &rdev->mc, base);
         rdev->mc.gtt_base_align = rdev->mc.gtt_size - 1;