drm/radeon: add spinlocks for indirect register accesss

This adds spinlocks to protect access to other
indirect register apertures.  These indirect spaces are
used pretty infrequently and we haven't had an reported
problems, but better safe than sorry.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/radeon/cik.c b/drivers/gpu/drm/radeon/cik.c
index 07aa13d..e521d4c 100644
--- a/drivers/gpu/drm/radeon/cik.c
+++ b/drivers/gpu/drm/radeon/cik.c
@@ -122,20 +122,27 @@
  */
 u32 cik_pciep_rreg(struct radeon_device *rdev, u32 reg)
 {
+	unsigned long flags;
 	u32 r;
 
+	spin_lock_irqsave(&rdev->pciep_idx_lock, flags);
 	WREG32(PCIE_INDEX, reg);
 	(void)RREG32(PCIE_INDEX);
 	r = RREG32(PCIE_DATA);
+	spin_unlock_irqrestore(&rdev->pciep_idx_lock, flags);
 	return r;
 }
 
 void cik_pciep_wreg(struct radeon_device *rdev, u32 reg, u32 v)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(&rdev->pciep_idx_lock, flags);
 	WREG32(PCIE_INDEX, reg);
 	(void)RREG32(PCIE_INDEX);
 	WREG32(PCIE_DATA, v);
 	(void)RREG32(PCIE_DATA);
+	spin_unlock_irqrestore(&rdev->pciep_idx_lock, flags);
 }
 
 static const u32 spectre_rlc_save_restore_register_list[] =