drm/radeon: Use RMW accessors for changing LNKCTL

Don't assume that only the driver would be accessing LNKCTL. ASPM policy
changes can trigger write to LNKCTL outside of driver's control.  And in
the case of upstream bridge, the driver does not even own the device it's
changing the registers for.

Use RMW capability accessors which do proper locking to avoid losing
concurrent updates to the register value.

Suggested-by: Lukas Wunner <lukas@wunner.de>
Fixes: 8a7cd27 ("drm/radeon/cik: add support for pcie gen1/2/3 switching")
Fixes: b9d305d ("drm/radeon: implement pcie gen2/3 support for SI")
Link: https://lore.kernel.org/r/20230717120503.15276-7-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>

Author: ij-intel

drivers/gpu/drm/radeon/cik.c

@@ -9534,17 +9534,8 @@ static void cik_pcie_gen3_enable(struct radeon_device *rdev)
 			u16 bridge_cfg2, gpu_cfg2;
 			u32 max_lw, current_lw, tmp;
 
-			pcie_capability_read_word(root, PCI_EXP_LNKCTL,
-						  &bridge_cfg);
-			pcie_capability_read_word(rdev->pdev, PCI_EXP_LNKCTL,
-						  &gpu_cfg);
-
-			tmp16 = bridge_cfg | PCI_EXP_LNKCTL_HAWD;
-			pcie_capability_write_word(root, PCI_EXP_LNKCTL, tmp16);
-
-			tmp16 = gpu_cfg | PCI_EXP_LNKCTL_HAWD;
-			pcie_capability_write_word(rdev->pdev, PCI_EXP_LNKCTL,
-						   tmp16);
+			pcie_capability_set_word(root, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_HAWD);
+			pcie_capability_set_word(rdev->pdev, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_HAWD);
 
 			tmp = RREG32_PCIE_PORT(PCIE_LC_STATUS1);
 			max_lw = (tmp & LC_DETECTED_LINK_WIDTH_MASK) >> LC_DETECTED_LINK_WIDTH_SHIFT;
@@ -9591,21 +9582,14 @@ static void cik_pcie_gen3_enable(struct radeon_device *rdev)
 				msleep(100);
 
 				/* linkctl */
-				pcie_capability_read_word(root, PCI_EXP_LNKCTL,
-							  &tmp16);
-				tmp16 &= ~PCI_EXP_LNKCTL_HAWD;
-				tmp16 |= (bridge_cfg & PCI_EXP_LNKCTL_HAWD);
-				pcie_capability_write_word(root, PCI_EXP_LNKCTL,
-							   tmp16);
-
-				pcie_capability_read_word(rdev->pdev,
-							  PCI_EXP_LNKCTL,
-							  &tmp16);
-				tmp16 &= ~PCI_EXP_LNKCTL_HAWD;
-				tmp16 |= (gpu_cfg & PCI_EXP_LNKCTL_HAWD);
-				pcie_capability_write_word(rdev->pdev,
-							   PCI_EXP_LNKCTL,
-							   tmp16);
+				pcie_capability_clear_and_set_word(root, PCI_EXP_LNKCTL,
+								   PCI_EXP_LNKCTL_HAWD,
+								   bridge_cfg &
+								   PCI_EXP_LNKCTL_HAWD);
+				pcie_capability_clear_and_set_word(rdev->pdev, PCI_EXP_LNKCTL,
+								   PCI_EXP_LNKCTL_HAWD,
+								   gpu_cfg &
+								   PCI_EXP_LNKCTL_HAWD);
 
 				/* linkctl2 */
 				pcie_capability_read_word(root, PCI_EXP_LNKCTL2,

drivers/gpu/drm/radeon/si.c

@@ -7131,17 +7131,8 @@ static void si_pcie_gen3_enable(struct radeon_device *rdev)
 			u16 bridge_cfg2, gpu_cfg2;
 			u32 max_lw, current_lw, tmp;
 
-			pcie_capability_read_word(root, PCI_EXP_LNKCTL,
-						  &bridge_cfg);
-			pcie_capability_read_word(rdev->pdev, PCI_EXP_LNKCTL,
-						  &gpu_cfg);
-
-			tmp16 = bridge_cfg | PCI_EXP_LNKCTL_HAWD;
-			pcie_capability_write_word(root, PCI_EXP_LNKCTL, tmp16);
-
-			tmp16 = gpu_cfg | PCI_EXP_LNKCTL_HAWD;
-			pcie_capability_write_word(rdev->pdev, PCI_EXP_LNKCTL,
-						   tmp16);
+			pcie_capability_set_word(root, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_HAWD);
+			pcie_capability_set_word(rdev->pdev, PCI_EXP_LNKCTL, PCI_EXP_LNKCTL_HAWD);
 
 			tmp = RREG32_PCIE(PCIE_LC_STATUS1);
 			max_lw = (tmp & LC_DETECTED_LINK_WIDTH_MASK) >> LC_DETECTED_LINK_WIDTH_SHIFT;
@@ -7188,22 +7179,14 @@ static void si_pcie_gen3_enable(struct radeon_device *rdev)
 				msleep(100);
 
 				/* linkctl */
-				pcie_capability_read_word(root, PCI_EXP_LNKCTL,
-							  &tmp16);
-				tmp16 &= ~PCI_EXP_LNKCTL_HAWD;
-				tmp16 |= (bridge_cfg & PCI_EXP_LNKCTL_HAWD);
-				pcie_capability_write_word(root,
-							   PCI_EXP_LNKCTL,
-							   tmp16);
-
-				pcie_capability_read_word(rdev->pdev,
-							  PCI_EXP_LNKCTL,
-							  &tmp16);
-				tmp16 &= ~PCI_EXP_LNKCTL_HAWD;
-				tmp16 |= (gpu_cfg & PCI_EXP_LNKCTL_HAWD);
-				pcie_capability_write_word(rdev->pdev,
-							   PCI_EXP_LNKCTL,
-							   tmp16);
+				pcie_capability_clear_and_set_word(root, PCI_EXP_LNKCTL,
+								   PCI_EXP_LNKCTL_HAWD,
+								   bridge_cfg &
+								   PCI_EXP_LNKCTL_HAWD);
+				pcie_capability_clear_and_set_word(rdev->pdev, PCI_EXP_LNKCTL,
+								   PCI_EXP_LNKCTL_HAWD,
+								   gpu_cfg &
+								   PCI_EXP_LNKCTL_HAWD);
 
 				/* linkctl2 */
 				pcie_capability_read_word(root, PCI_EXP_LNKCTL2,