[ppc440SPe] Graceful recovery from machine check during PCIe configuration

During config transactions on the PCIe bus an attempt to scan for a
non-existent device can lead to a machine check exception with certain
peripheral devices. In order to avoid crashing in such scenarios the
instrumented versions of the config cycle read routines are introduced, so
the exceptions fixups framework can gracefully recover.

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Acked-by: Rafal Jaworowski <raj@semihalf.com>

cpu/ppc4xx/440spe_pcie.c

@@ -1,5 +1,5 @@
 /*
- * (C) Copyright 2006
+ * (C) Copyright 2006 - 2007
  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
  *
  * Copyright (c) 2005 Cisco Systems.  All rights reserved.
@@ -40,6 +40,34 @@ enum {
 	LNKW_X8			= 0x8
 };
 
+static inline int pcie_in_8(const volatile unsigned char __iomem *addr)
+{
+	int ret;
+
+	PCIE_IN(lbzx, ret, addr);
+
+	return ret;
+}
+
+static inline int pcie_in_le16(const volatile unsigned short __iomem *addr)
+{
+	int ret;
+
+	PCIE_IN(lhbrx, ret, addr)
+
+	return ret;
+}
+
+static inline unsigned pcie_in_le32(const volatile unsigned __iomem *addr)
+{
+	unsigned ret;
+
+	PCIE_IN(lwbrx, ret, addr);
+
+	return ret;
+}
+
+
 static int pcie_read_config(struct pci_controller *hose, unsigned int devfn,
 	int offset, int len, u32 *val) {
 
@@ -55,13 +83,13 @@ static int pcie_read_config(struct pci_controller *hose, unsigned int devfn,
 
 	switch (len) {
 	case 1:
-		*val = in_8(hose->cfg_data + offset);
+		*val = pcie_in_8(hose->cfg_data + offset);
 		break;
 	case 2:
-		*val = in_le16((u16 *)(hose->cfg_data + offset));
+		*val = pcie_in_le16((u16 *)(hose->cfg_data + offset));
 		break;
 	default:
-		*val = in_le32((u32 *)(hose->cfg_data + offset));
+		*val = pcie_in_le32((u32*)(hose->cfg_data + offset));
 		break;
 	}
 	return 0;

cpu/ppc4xx/440spe_pcie.h

@@ -145,8 +145,8 @@
 #define PECFG_PIMEN		0x33c
 #define PECFG_PIM0LAL		0x340
 #define PECFG_PIM0LAH		0x344
-#define PECFG_PIM1LAL     	0x348
-#define PECFG_PIM1LAH     	0x34c
+#define PECFG_PIM1LAL		0x348
+#define PECFG_PIM1LAH		0x34c
 #define PECFG_PIM01SAL		0x350
 #define PECFG_PIM01SAH		0x354
 
@@ -161,6 +161,21 @@
 	mtdcr(DCRN_SDR0_CFGADDR, offset); \
 	mtdcr(DCRN_SDR0_CFGDATA,data);})
 
+#define PCIE_IN(opcode, ret, addr) \
+	__asm__ __volatile__(			\
+		"sync\n"			\
+		#opcode " %0,0,%1\n"		\
+		"1: twi 0,%0,0\n"		\
+		"isync\n"			\
+		"b 3f\n"			\
+		"2: li %0,-1\n"			\
+		"3:\n"				\
+		".section __ex_table,\"a\"\n"	\
+		".balign 4\n"			\
+		".long 1b,2b\n"			\
+		".previous\n"			\
+		: "=r" (ret) : "r" (addr), "m" (*addr));
+
 int ppc440spe_init_pcie(void);
 int ppc440spe_init_pcie_rootport(int port);
 void yucca_setup_pcie_fpga_rootpoint(int port);

cpu/ppc4xx/traps.c

@@ -151,12 +151,17 @@ MachineCheckException(struct pt_regs *regs)
 	int uncorr_ecc = 0;
 #endif
 
-	/* Probing PCI using config cycles cause this exception
-	 * when a device is not present.  Catch it and return to
-	 * the PCI exception handler.
+	/* Probing PCI(E) using config cycles may cause this exception
+	 * when a device is not present. To gracefully recover in such
+	 * scenarios config read/write routines need to be instrumented in
+	 * order to return via fixup handler. For examples refer to
+	 * pcie_in_8(), pcie_in_le16() and pcie_in_le32()
 	 */
 	if ((fixup = search_exception_table(regs->nip)) != 0) {
 		regs->nip = fixup;
+		val = mfspr(MCSR);
+		/* Clear MCSR */
+                mtspr(SPRN_MCSR, val);
 		return;
 	}
 

lib_ppc/extable.c

@@ -89,7 +89,7 @@ search_exception_table(unsigned long addr)
 	/* if the serial port does not hang in exception, printf can be used */
 #if !defined(CFG_SERIAL_HANG_IN_EXCEPTION)
 	if (ex_tab_message)
-		printf("Bus Fault @ 0x%08lx, fixup 0x%08lx\n", addr, ret);
+		debug("Bus Fault @ 0x%08lx, fixup 0x%08lx\n", addr, ret);
 #endif
 	if (ret) return ret;