mpc83xx: fix PCI scan hang on the standalone MPC837xE-MDS boards

The MPC837xE-MDS board's CPLD can auto-detect if the board is on the PIB,
standalone or acting as a PCI agent. User's Guide says:

- When the CPLD recognizes its location on the PIB it automatically
  configures RCW to the PCI Host.
- If the CPLD fails to recognize its location then it is automatically
  configured as an Agent and the PCI is configured to an external arbiter.

This sounds good. Though in the standalone setup the CPLD sets PCI_HOST
flag (it's ok, we can't act as PCI agents since we receive CLKIN, not
PCICLK), but the CPLD doesn't set the ARBITER_ENABLE flag, and without
any arbiter bad things will happen (here the board hangs during any config
space reads).

In this situation we must disable the PCI. And in case of anybody really
want to use an external arbiter, we provide "pci_external_aribter"
environment variable.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>

board/freescale/mpc837xemds/mpc837xemds.c

@@ -270,6 +270,45 @@ int checkboard(void)
 	return 0;
 }
 
+#ifdef CONFIG_PCI
+int board_pci_host_broken(void)
+{
+	struct immap __iomem *im = (struct immap __iomem *)CONFIG_SYS_IMMR;
+	const u32 rcw_mask = HRCWH_PCI1_ARBITER_ENABLE | HRCWH_PCI_HOST;
+	const char *pci_ea = getenv("pci_external_arbiter");
+
+	/* It's always OK in case of external arbiter. */
+	if (pci_ea && !strcmp(pci_ea, "yes"))
+		return 0;
+
+	if ((in_be32(&im->reset.rcwh) & rcw_mask) != rcw_mask)
+		return 1;
+
+	return 0;
+}
+
+static void ft_pci_fixup(void *blob, bd_t *bd)
+{
+	const char *status = "broken (no arbiter)";
+	int off;
+	int err;
+
+	off = fdt_path_offset(blob, "pci0");
+	if (off < 0) {
+		printf("WARNING: could not find pci0 alias: %s.\n",
+			fdt_strerror(off));
+		return;
+	}
+
+	err = fdt_setprop(blob, off, "status", status, strlen(status) + 1);
+	if (err) {
+		printf("WARNING: could not set status for pci0: %s.\n",
+			fdt_strerror(err));
+		return;
+	}
+}
+#endif
+
 #if defined(CONFIG_OF_BOARD_SETUP)
 void ft_board_setup(void *blob, bd_t *bd)
 {
@@ -277,6 +316,8 @@ void ft_board_setup(void *blob, bd_t *bd)
 	ft_tsec_fixup(blob, bd);
 #ifdef CONFIG_PCI
 	ft_pci_setup(blob, bd);
+	if (board_pci_host_broken())
+		ft_pci_fixup(blob, bd);
 #endif
 }
 #endif /* CONFIG_OF_BOARD_SETUP */

board/freescale/mpc837xemds/pci.c

@@ -47,6 +47,9 @@ void pci_init_board(void)
 	volatile law83xx_t *pci_law = immr->sysconf.pcilaw;
 	struct pci_region *reg[] = { pci_regions };
 
+	if (board_pci_host_broken())
+		return;
+
 	/* Enable all 5 PCI_CLK_OUTPUTS */
 	clk->occr |= 0xf8000000;
 	udelay(2000);

include/configs/MPC837XEMDS.h

@@ -348,6 +348,9 @@
 #define CONFIG_SYS_PCI_SLV_MEM_SIZE	0x80000000
 
 #ifdef CONFIG_PCI
+#ifndef __ASSEMBLY__
+extern int board_pci_host_broken(void);
+#endif
 #define CONFIG_83XX_GENERIC_PCI	1 /* Use generic PCI setup */
 #define CONFIG_PQ_MDS_PIB	1 /* PQ MDS Platform IO Board */