powerpc/mpc5200: PCI write combine timer

On MPC5200 the PCI target control register (PCITCR) @ MBAR + 0xD6C is
initialized with only bit 7 (Latrule disable) set. The 8-Bit write
combine timer (Bits 24..31) should be also set to a reasonable value
_greater zero_ (0x08 = default) since setting it to 0x00 leads to
_very poor_ performance as a PCI target since external burst won't be
possible at all.

Setting the WCT to 0x08 (cache-line size) leads to good overall perfomance.
Signed-off-by: NAndre Schwarz <andre.schwarz@matrix-vision.de>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

arch/powerpc/platforms/52xx/mpc52xx_pci.c

@@ -63,6 +63,7 @@
 
 #define MPC52xx_PCI_TCR_P		0x01000000
 #define MPC52xx_PCI_TCR_LD		0x00010000
+#define MPC52xx_PCI_TCR_WCT8		0x00000008
 
 #define MPC52xx_PCI_TBATR_DISABLE	0x0
 #define MPC52xx_PCI_TBATR_ENABLE	0x1
@@ -313,7 +314,7 @@ mpc52xx_pci_setup(struct pci_controller *hose,
 	out_be32(&pci_regs->tbatr1,
 		MPC52xx_PCI_TBATR_ENABLE | MPC52xx_PCI_TARGET_MEM );
 
-	out_be32(&pci_regs->tcr, MPC52xx_PCI_TCR_LD);
+	out_be32(&pci_regs->tcr, MPC52xx_PCI_TCR_LD | MPC52xx_PCI_TCR_WCT8);
 
 	tmp = in_be32(&pci_regs->gscr);
 #if 0