[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>

diff --git a/arch/powerpc/platforms/pasemi/pci.c b/arch/powerpc/platforms/pasemi/pci.c
index fcfb3df3f1a947aa3b2711effbd42e097995bf79..b6a0ec45c69554c7558ec45f478ce40b5cf1411c 100644 (file)
--- 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);
 }