[POWERPC] pasemi: Add workaround for erratum 5945

Erratum 5945 causes some of the registers on the PCIe root ports to
not read correctly.  Do a small dance to avoid this: Write an unused
register, read the value and write it back.  Thankfully this is not in
a hot code path.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 60 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/pasemi/pci.c b/arch/powerpc/platforms/pasemi/pci.c
index fcfb3df3f1a9..b6a0ec45c695 100644
--- a/arch/powerpc/platforms/pasemi/pci.c
+++ b/arch/powerpc/platforms/pasemi/pci.c
@@ -51,6 +51,61 @@ static void volatile __iomem *pa_pxp_cfg_addr(struct pci_controller *hose,
         return hose->cfg_data + PA_PXP_CFA(bus, devfn, offset);
 }
 
+static inline int is_root_port(int busno, int devfn)
+{
+        return ((busno == 0) && (PCI_FUNC(devfn) < 4) &&
+                 ((PCI_SLOT(devfn) == 16) || (PCI_SLOT(devfn) == 17)));
+}
+
+static inline int is_5945_reg(int reg)
+{
+        return (((reg >= 0x18) && (reg < 0x34)) ||
+                ((reg >= 0x158) && (reg < 0x178)));
+}
+
+static int workaround_5945(struct pci_bus *bus, unsigned int devfn,
+                           int offset, int len, u32 *val)
+{
+        struct pci_controller *hose;
+        void volatile __iomem *addr, *dummy;
+        int byte;
+        u32 tmp;
+
+        if (!is_root_port(bus->number, devfn) || !is_5945_reg(offset))
+                return 0;
+
+        hose = pci_bus_to_host(bus);
+
+        addr = pa_pxp_cfg_addr(hose, bus->number, devfn, offset & ~0x3);
+        byte = offset & 0x3;
+
+        /* Workaround bug 5945: write 0 to a dummy register before reading,
+         * and write back what we read. We must read/write the full 32-bit
+         * contents so we need to shift and mask by hand.
+         */
+        dummy = pa_pxp_cfg_addr(hose, bus->number, devfn, 0x10);
+        out_le32(dummy, 0);
+        tmp = in_le32(addr);
+        out_le32(addr, tmp);
+
+        switch (len) {
+        case 1:
+                *val = (tmp >> (8*byte)) & 0xff;
+                break;
+        case 2:
+                if (byte == 0)
+                        *val = tmp & 0xffff;
+                else
+                        *val = (tmp >> 16) & 0xffff;
+                break;
+        default:
+                *val = tmp;
+                break;
+        }
+
+        return 1;
+}
+
 static int pa_pxp_read_config(struct pci_bus *bus, unsigned int devfn,
                               int offset, int len, u32 *val)
 {
@@ -64,6 +119,9 @@ static int pa_pxp_read_config(struct pci_bus *bus, unsigned int devfn,
         if (!pa_pxp_offset_valid(bus->number, devfn, offset))
                 return PCIBIOS_BAD_REGISTER_NUMBER;
 
+        if (workaround_5945(bus, devfn, offset, len, val))
+                return PCIBIOS_SUCCESSFUL;
+
         addr = pa_pxp_cfg_addr(hose, bus->number, devfn, offset);
 
         /*
@@ -180,7 +238,7 @@ void __iomem *pasemi_pci_getcfgaddr(struct pci_dev *dev, int offset)
 {
         struct pci_controller *hose;
 
-        hose = pci_bus_to_host(bus);
+        hose = pci_bus_to_host(dev->bus);
 
-        return pa_pxp_cfg_addr(hose, hose->number, dev->devfn, int offset)
+        return (void __iomem *)pa_pxp_cfg_addr(hose, dev->bus->number, dev->devfn, offset);
 }