2 files changed, 47 insertions, 1 deletions

diff --git a/arch/ia64/sn/pci/pci_dma.c b/arch/ia64/sn/pci/pci_dma.c
index 0e4b9ad9ef02..abdf6eea6ac8 100644
--- a/arch/ia64/sn/pci/pci_dma.c
+++ b/arch/ia64/sn/pci/pci_dma.c
@@ -326,6 +326,29 @@ int sn_pci_legacy_read(struct pci_bus *bus, u16 port, u32 *val, u8 size)
 {
         unsigned long addr;
         int ret;
+        struct ia64_sal_retval isrv;
+
+        /*
+         * First, try the SN_SAL_IOIF_PCI_SAFE SAL call which can work
+         * around hw issues at the pci bus level.  SGI proms older than
+         * 4.10 don't implment this.
+         */
+
+        SAL_CALL(isrv, SN_SAL_IOIF_PCI_SAFE,
+                pci_domain_nr(bus), bus->number,
+                0, /* io */
+                0, /* read */
+                port, size, __pa(val));
+
+        if (isrv.status == 0)
+                return size;
+
+        /*
+         * If the above failed, retry using the SAL_PROBE call which should
+         * be present in all proms (but which cannot work round PCI chipset
+         * bugs).  This code is retained for compatability with old
+         * pre-4.10 proms, and should be removed at some point in the future.
+         */
 
         if (!SN_PCIBUS_BUSSOFT(bus))
                 return -ENODEV;
@@ -349,6 +372,29 @@ int sn_pci_legacy_write(struct pci_bus *bus, u16 port, u32 val, u8 size)
         int ret = size;
         unsigned long paddr;
         unsigned long *addr;
+        struct ia64_sal_retval isrv;
+
+        /*
+         * First, try the SN_SAL_IOIF_PCI_SAFE SAL call which can work
+         * around hw issues at the pci bus level.  SGI proms older than
+         * 4.10 don't implment this.
+         */
+
+        SAL_CALL(isrv, SN_SAL_IOIF_PCI_SAFE,
+                pci_domain_nr(bus), bus->number,
+                0, /* io */
+                1, /* write */
+                port, size, __pa(&val));
+
+        if (isrv.status == 0)
+                return size;
+
+        /*
+         * If the above failed, retry using the SAL_PROBE call which should
+         * be present in all proms (but which cannot work round PCI chipset
+         * bugs).  This code is retained for compatability with old
+         * pre-4.10 proms, and should be removed at some point in the future.
+         */
 
         if (!SN_PCIBUS_BUSSOFT(bus)) {
                 ret = -ENODEV;
diff --git a/include/asm-ia64/sn/sn_sal.h b/include/asm-ia64/sn/sn_sal.h
index fea35b33d4e4..b2d32837723f 100644
--- a/include/asm-ia64/sn/sn_sal.h
+++ b/include/asm-ia64/sn/sn_sal.h
@@ -67,7 +67,7 @@
 #define  SN_SAL_IOIF_INTERRUPT                     0x0200004a
 #define  SN_SAL_HWPERF_OP                          0x02000050   // lock
 #define  SN_SAL_IOIF_ERROR_INTERRUPT               0x02000051
-
+#define  SN_SAL_IOIF_PCI_SAFE                      0x02000052
 #define  SN_SAL_IOIF_SLOT_ENABLE                   0x02000053
 #define  SN_SAL_IOIF_SLOT_DISABLE                  0x02000054
 #define  SN_SAL_IOIF_GET_HUBDEV_INFO               0x02000055