[PATCH] drm/radeon/kms: make sure pci max read request size is valid on evergreen+

[alexdeucher@gmail.com]

From: Alex Deucher <alexander.deucher@amd.com>

If the bios or OS sets the pci max read request size to 0 or an
invalid value (6,7), it can result in a hang or slowdown.  Check
and set it to something sane if it's invalid.

Fixes:
https://bugzilla.kernel.org/show_bug.cgi?id=42162

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@kernel.org
---
 drivers/gpu/drm/radeon/evergreen.c |   24 ++++++++++++++++++++++++
 drivers/gpu/drm/radeon/ni.c        |    3 +++
 2 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/radeon/evergreen.c b/drivers/gpu/drm/radeon/evergreen.c
index d8b725d..1e040f5 100644
--- a/drivers/gpu/drm/radeon/evergreen.c
+++ b/drivers/gpu/drm/radeon/evergreen.c
@@ -41,6 +41,28 @@ static void evergreen_gpu_init(struct radeon_device *rdev);
 void evergreen_fini(struct radeon_device *rdev);
 static void evergreen_pcie_gen2_enable(struct radeon_device *rdev);
 
+#define PCI_DEVICE_CNTL 0x60
+#define PCI_MAX_READ_REQUEST_SIZE_SHIFT 12
+#define PCI_MAX_READ_REQUEST_SIZE_MASK  (7 << 12)
+
+void evergreen_fix_pci_max_read_req_size(struct radeon_device *rdev)
+{
+	u16 tmp;
+
+	pci_read_config_word(rdev->pdev, PCI_DEVICE_CNTL, &tmp);
+
+	/* if bios or OS sets MAX_READ_REQUEST_SIZE to an invalid value, fix it
+	 * to avoid hangs or perfomance issues
+	 */
+	if ((((tmp & PCI_MAX_READ_REQUEST_SIZE_MASK) >> PCI_MAX_READ_REQUEST_SIZE_SHIFT) == 0) ||
+	    (((tmp & PCI_MAX_READ_REQUEST_SIZE_MASK) >> PCI_MAX_READ_REQUEST_SIZE_SHIFT) == 6) ||
+	    (((tmp & PCI_MAX_READ_REQUEST_SIZE_MASK) >> PCI_MAX_READ_REQUEST_SIZE_SHIFT) == 7)) {
+		tmp &= ~PCI_MAX_READ_REQUEST_SIZE_MASK;
+		tmp |= (2 << PCI_MAX_READ_REQUEST_SIZE_SHIFT);
+		pci_write_config_word(rdev->pdev, PCI_DEVICE_CNTL, tmp);
+	}
+}
+
 void evergreen_pre_page_flip(struct radeon_device *rdev, int crtc)
 {
 	/* enable the pflip int */
@@ -1865,6 +1887,8 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
 
 	WREG32(GRBM_CNTL, GRBM_READ_TIMEOUT(0xff));
 
+	evergreen_fix_pci_max_read_req_size(rdev);
+
 	cc_gc_shader_pipe_config = RREG32(CC_GC_SHADER_PIPE_CONFIG) & ~2;
 
 	cc_gc_shader_pipe_config |=
diff --git a/drivers/gpu/drm/radeon/ni.c b/drivers/gpu/drm/radeon/ni.c
index d916c82..d6cb534 100644
--- a/drivers/gpu/drm/radeon/ni.c
+++ b/drivers/gpu/drm/radeon/ni.c
@@ -39,6 +39,7 @@ extern int evergreen_mc_wait_for_idle(struct radeon_device *rdev);
 extern void evergreen_mc_program(struct radeon_device *rdev);
 extern void evergreen_irq_suspend(struct radeon_device *rdev);
 extern int evergreen_mc_init(struct radeon_device *rdev);
+extern void evergreen_fix_pci_max_read_req_size(struct radeon_device *rdev);
 
 #define EVERGREEN_PFP_UCODE_SIZE 1120
 #define EVERGREEN_PM4_UCODE_SIZE 1376
@@ -724,6 +725,8 @@ static void cayman_gpu_init(struct radeon_device *rdev)
 
 	WREG32(GRBM_CNTL, GRBM_READ_TIMEOUT(0xff));
 
+	evergreen_fix_pci_max_read_req_size(rdev);
+
 	mc_shared_chmap = RREG32(MC_SHARED_CHMAP);
 	mc_arb_ramcfg = RREG32(MC_ARB_RAMCFG);
 
-- 
1.7.1.1