SB1 cache exception handling.

    
Expand SB1 cache error handling by adding SB1_CEX_ALWAYS_FATAL and
SB1_CEX_STALL, allowing configurable behavior on cache errors.
    
Signed-Off-By: Andy Isaacson <adi@broadcom.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

3 files changed, 59 insertions, 8 deletions

diff --git a/arch/mips/mm/cerr-sb1.c b/arch/mips/mm/cerr-sb1.c
index 7166ffe63502..1cf3c6006ccd 100644
--- a/arch/mips/mm/cerr-sb1.c
+++ b/arch/mips/mm/cerr-sb1.c
@@ -19,13 +19,19 @@
 #include <linux/sched.h>
 #include <asm/mipsregs.h>
 #include <asm/sibyte/sb1250.h>
+#include <asm/sibyte/sb1250_regs.h>
 
-#ifndef CONFIG_SIBYTE_BUS_WATCHER
+#if !defined(CONFIG_SIBYTE_BUS_WATCHER) || defined(CONFIG_SIBYTE_BW_TRACE)
 #include <asm/io.h>
-#include <asm/sibyte/sb1250_regs.h>
 #include <asm/sibyte/sb1250_scd.h>
 #endif
 
+/*
+ * We'd like to dump the L2_ECC_TAG register on errors, but errata make
+ * that unsafe... So for now we don't.  (BCM1250/BCM112x erratum SOC-48.)
+ */
+#undef DUMP_L2_ECC_TAG_ON_ERROR
+
 /* SB1 definitions */
 
 /* XXX should come from config1 XXX */
@@ -139,12 +145,18 @@ static inline void breakout_cerrd(unsigned int val)
 static void check_bus_watcher(void)
 {
         uint32_t status, l2_err, memio_err;
+#ifdef DUMP_L2_ECC_TAG_ON_ERROR
+        uint64_t l2_tag;
+#endif
 
         /* Destructive read, clears register and interrupt */
         status = csr_in32(IOADDR(A_SCD_BUS_ERR_STATUS));
         /* Bit 31 is always on, but there's no #define for that */
         if (status & ~(1UL << 31)) {
                 l2_err = csr_in32(IOADDR(A_BUS_L2_ERRORS));
+#ifdef DUMP_L2_ECC_TAG_ON_ERROR
+                l2_tag = in64(IO_SPACE_BASE | A_L2_ECC_TAG);
+#endif
                 memio_err = csr_in32(IOADDR(A_BUS_MEM_IO_ERRORS));
                 prom_printf("Bus watcher error counters: %08x %08x\n", l2_err, memio_err);
                 prom_printf("\nLast recorded signature:\n");
@@ -153,6 +165,9 @@ static void check_bus_watcher(void)
                        (int)(G_SCD_BERR_TID(status) >> 6),
                        (int)G_SCD_BERR_RID(status),
                        (int)G_SCD_BERR_DCODE(status));
+#ifdef DUMP_L2_ECC_TAG_ON_ERROR
+                prom_printf("Last L2 tag w/ bad ECC: %016llx\n", l2_tag);
+#endif
         } else {
                 prom_printf("Bus watcher indicates no error\n");
         }
@@ -166,6 +181,16 @@ asmlinkage void sb1_cache_error(void)
         uint64_t cerr_dpa;
         uint32_t errctl, cerr_i, cerr_d, dpalo, dpahi, eepc, res;
 
+#ifdef CONFIG_SIBYTE_BW_TRACE
+        /* Freeze the trace buffer now */
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+        csr_out32(M_BCM1480_SCD_TRACE_CFG_FREEZE, IO_SPACE_BASE | A_SCD_TRACE_CFG);
+#else
+        csr_out32(M_SCD_TRACE_CFG_FREEZE, IO_SPACE_BASE | A_SCD_TRACE_CFG);
+#endif
+        prom_printf("Trace buffer frozen\n");
+#endif
+
         prom_printf("Cache error exception on CPU %x:\n",
                     (read_c0_prid() >> 25) & 0x7);
 
@@ -229,11 +254,19 @@ asmlinkage void sb1_cache_error(void)
 
         check_bus_watcher();
 
-        while (1);
         /*
-         * This tends to make things get really ugly; let's just stall instead.
-         *    panic("Can't handle the cache error!");
+         * Calling panic() when a fatal cache error occurs scrambles the
+         * state of the system (and the cache), making it difficult to
+         * investigate after the fact.  However, if you just stall the CPU,
+         * the other CPU may keep on running, which is typically very
+         * undesirable.
          */
+#ifdef CONFIG_SB1_CERR_STALL
+        while (1)
+                ;
+#else
+        panic("unhandled cache error");
+#endif
 }
 
 
@@ -434,7 +467,8 @@ static struct dc_state dc_states[] = {
 };
 
 #define DC_TAG_VALID(state) \
-    (((state) == 0xf) || ((state) == 0x13) || ((state) == 0x19) || ((state == 0x16)) || ((state) == 0x1c))
+    (((state) == 0x0) || ((state) == 0xf) || ((state) == 0x13) || \
+     ((state) == 0x19) || ((state) == 0x16) || ((state) == 0x1c))
 
 static char *dc_state_str(unsigned char state)
 {
@@ -505,6 +539,7 @@ static uint32_t extract_dc(unsigned short addr, int data)
                         uint64_t datalo;
                         uint32_t datalohi, datalolo, datahi;
                         int offset;
+                        char bad_ecc = 0;
 
                         for (offset = 0; offset < 4; offset++) {
                                 /* Index-load-data-D */
@@ -525,8 +560,7 @@ static uint32_t extract_dc(unsigned short addr, int data)
                                 ecc = dc_ecc(datalo);
                                 if (ecc != datahi) {
                                         int bits = 0;
-                                        prom_printf("  ** bad ECC (%02x %02x) ->",
-                                                    datahi, ecc);
+                                        bad_ecc |= 1 << (3-offset);
                                         ecc ^= datahi;
                                         while (ecc) {
                                                 if (ecc & 1) bits++;
@@ -537,6 +571,10 @@ static uint32_t extract_dc(unsigned short addr, int data)
                                 prom_printf("  %02X-%016llX", datahi, datalo);
                         }
                         prom_printf("\n");
+                        if (bad_ecc)
+                                prom_printf("  dwords w/ bad ECC: %d %d %d %d\n",
+                                            !!(bad_ecc & 8), !!(bad_ecc & 4),
+                                            !!(bad_ecc & 2), !!(bad_ecc & 1));
                 }
         }
         return res;
diff --git a/arch/mips/mm/cex-sb1.S b/arch/mips/mm/cex-sb1.S
index 2c3a23aa88c3..0e71580774ff 100644
--- a/arch/mips/mm/cex-sb1.S
+++ b/arch/mips/mm/cex-sb1.S
@@ -64,6 +64,10 @@ LEAF(except_vec2_sb1)
         sd      k0,0x170($0)
         sd      k1,0x178($0)
 
+#if CONFIG_SB1_CEX_ALWAYS_FATAL
+        j       handle_vec2_sb1
+         nop
+#else
         /*
          * M_ERRCTL_RECOVERABLE is bit 31, which makes it easy to tell
          * if we can fast-path out of here for a h/w-recovered error.
@@ -134,6 +138,7 @@ unrecoverable:
         /* Unrecoverable Icache or Dcache error; log it and/or fail */
         j       handle_vec2_sb1
          nop
+#endif
 
 END(except_vec2_sb1)
 
diff --git a/arch/mips/sibyte/Kconfig b/arch/mips/sibyte/Kconfig
index 6a5a08f5e212..de46f62ac462 100644
--- a/arch/mips/sibyte/Kconfig
+++ b/arch/mips/sibyte/Kconfig
@@ -102,6 +102,14 @@ config SIMULATION
           Build a kernel suitable for running under the GDB simulator.
           Primarily adjusts the kernel's notion of time.
 
+config CONFIG_SB1_CEX_ALWAYS_FATAL
+        bool "All cache exceptions considered fatal (no recovery attempted)"
+        depends on SIBYTE_SB1xxx_SOC
+
+config CONFIG_SB1_CERR_STALL
+        bool "Stall (rather than panic) on fatal cache error"
+        depends on SIBYTE_SB1xxx_SOC
+
 config SIBYTE_CFE
         bool "Booting from CFE"
         depends on SIBYTE_SB1xxx_SOC