x86/amd-iommu: Work around S3 BIOS bug

This patch adds a workaround for an IOMMU BIOS problem to
the AMD IOMMU driver. The result of the bug is that the
IOMMU does not execute commands anymore when the system
comes out of the S3 state resulting in system failure. The
bug in the BIOS is that is does not restore certain hardware
specific registers correctly. This workaround reads out the
contents of these registers at boot time and restores them
on resume from S3. The workaround is limited to the specific
IOMMU chipset where this problem occurs.

Cc: stable@kernel.org
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

3 files changed, 33 insertions, 0 deletions

diff --git a/arch/x86/include/asm/amd_iommu_proto.h b/arch/x86/include/asm/amd_iommu_proto.h
index d2544f1d705d..cb030374b90a 100644
--- a/arch/x86/include/asm/amd_iommu_proto.h
+++ b/arch/x86/include/asm/amd_iommu_proto.h
@@ -38,4 +38,10 @@ static inline void amd_iommu_stats_init(void) { }
 
 #endif /* !CONFIG_AMD_IOMMU_STATS */
 
+static inline bool is_rd890_iommu(struct pci_dev *pdev)
+{
+        return (pdev->vendor == PCI_VENDOR_ID_ATI) &&
+               (pdev->device == PCI_DEVICE_ID_RD890_IOMMU);
+}
+
 #endif /* _ASM_X86_AMD_IOMMU_PROTO_H  */
diff --git a/arch/x86/include/asm/amd_iommu_types.h b/arch/x86/include/asm/amd_iommu_types.h
index ef2d5cd7d7e7..08616180deaf 100644
--- a/arch/x86/include/asm/amd_iommu_types.h
+++ b/arch/x86/include/asm/amd_iommu_types.h
@@ -414,6 +414,15 @@ struct amd_iommu {
 
         /* default dma_ops domain for that IOMMU */
         struct dma_ops_domain *default_dom;
+
+        /*
+         * This array is required to work around a potential BIOS bug.
+         * The BIOS may miss to restore parts of the PCI configuration
+         * space when the system resumes from S3. The result is that the
+         * IOMMU does not execute commands anymore which leads to system
+         * failure.
+         */
+        u32 cache_cfg[4];
 };
 
 /*
diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 85e9817ead43..5a170cbbbed8 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -632,6 +632,13 @@ static void __init init_iommu_from_pci(struct amd_iommu *iommu)
         iommu->last_device = calc_devid(MMIO_GET_BUS(range),
                                         MMIO_GET_LD(range));
         iommu->evt_msi_num = MMIO_MSI_NUM(misc);
+
+        if (is_rd890_iommu(iommu->dev)) {
+                pci_read_config_dword(iommu->dev, 0xf0, &iommu->cache_cfg[0]);
+                pci_read_config_dword(iommu->dev, 0xf4, &iommu->cache_cfg[1]);
+                pci_read_config_dword(iommu->dev, 0xf8, &iommu->cache_cfg[2]);
+                pci_read_config_dword(iommu->dev, 0xfc, &iommu->cache_cfg[3]);
+        }
 }
 
 /*
@@ -1120,6 +1127,16 @@ static void iommu_init_flags(struct amd_iommu *iommu)
         iommu_feature_enable(iommu, CONTROL_COHERENT_EN);
 }
 
+static void iommu_apply_quirks(struct amd_iommu *iommu)
+{
+        if (is_rd890_iommu(iommu->dev)) {
+                pci_write_config_dword(iommu->dev, 0xf0, iommu->cache_cfg[0]);
+                pci_write_config_dword(iommu->dev, 0xf4, iommu->cache_cfg[1]);
+                pci_write_config_dword(iommu->dev, 0xf8, iommu->cache_cfg[2]);
+                pci_write_config_dword(iommu->dev, 0xfc, iommu->cache_cfg[3]);
+        }
+}
+
 /*
  * This function finally enables all IOMMUs found in the system after
  * they have been initialized
@@ -1130,6 +1147,7 @@ static void enable_iommus(void)
 
         for_each_iommu(iommu) {
                 iommu_disable(iommu);
+                iommu_apply_quirks(iommu);
                 iommu_init_flags(iommu);
                 iommu_set_device_table(iommu);
                 iommu_enable_command_buffer(iommu);