[PATCH] iommu/amd: Expicitly enable CNTRL.EPHEn bit in resume path

[Vasant Hegde <vasant.hegde@amd.com>]

With recent kernel, AMDGPU failed to resume after suspend on certain laptop.

Sample log:
-----------
Nov 14 11:52:19 Thinkbook kernel: iommu ivhd0: AMD-Vi: Event logged [ILLEGAL_DEV_TABLE_ENTRY device=0000:06:00.0 pasid=0x00000 address=0x135300000 flags=0x0080]
Nov 14 11:52:19 Thinkbook kernel: AMD-Vi: DTE[0]: 7d90000000000003
Nov 14 11:52:19 Thinkbook kernel: AMD-Vi: DTE[1]: 0000100103fc0009
Nov 14 11:52:19 Thinkbook kernel: AMD-Vi: DTE[2]: 2000000117840013
Nov 14 11:52:19 Thinkbook kernel: AMD-Vi: DTE[3]: 0000000000000000

This is because in resume path, CNTRL[EPHEn] is not set. Fix this by
setting CNTRL[EPHEn] to 1 in resume path if EFR[EPHSUP] is set.

Note
  May be better approach is to save the control register in suspend path
  and restore it in resume path instead of trying to set indivisual
  bits. We will have separate patch for that.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219499
Fixes: c4cb2311110 ("iommu/amd: Add support for enable/disable IOPF")
Tested-by: Hamish McIntyre-Bhatty <kernel-bugzilla@regd.hamishmb.com>
Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
---
 drivers/iommu/amd/amd_iommu_types.h | 1 +
 drivers/iommu/amd/init.c            | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 0bbda60d3cdc..23caea22f8dc 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -175,6 +175,7 @@
 #define CONTROL_GAM_EN		25
 #define CONTROL_GALOG_EN	28
 #define CONTROL_GAINT_EN	29
+#define CONTROL_EPH_EN		45
 #define CONTROL_XT_EN		50
 #define CONTROL_INTCAPXT_EN	51
 #define CONTROL_IRTCACHEDIS	59
diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index c5cd92edada0..438848b0682f 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -2653,6 +2653,10 @@ static void iommu_init_flags(struct amd_iommu *iommu)
 
 	/* Set IOTLB invalidation timeout to 1s */
 	iommu_set_inv_tlb_timeout(iommu, CTRL_INV_TO_1S);
+
+	/* Enable Enhanced Peripheral Page Request Handling */
+	if (check_feature(FEATURE_EPHSUP))
+		iommu_feature_enable(iommu, CONTROL_EPH_EN);
 }
 
 static void iommu_apply_resume_quirks(struct amd_iommu *iommu)
-- 
2.31.1