Blackfin arch: Add ability to expend the hardware trace buffer

Add ability to expend the hardware trace buffer via a configurable
software buffer - so you can have lots of history when a crash occurs.

The interesting way we do printk in the traps.c confusese the checking
script

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

1 files changed, 73 insertions, 0 deletions

diff --git a/arch/blackfin/mach-common/entry.S b/arch/blackfin/mach-common/entry.S
index 207e69786b40..ab278a72f282 100644
--- a/arch/blackfin/mach-common/entry.S
+++ b/arch/blackfin/mach-common/entry.S
@@ -731,6 +731,75 @@ ENTRY(_init_exception_buff)
         rts;
 ENDPROC(_init_exception_buff)
 
+/* We handle this 100% in exception space - to reduce overhead
+ * Only potiential problem is if the software buffer gets swapped out of the
+ * CPLB table - then double fault. - so we don't let this happen in other places
+ */
+#ifdef CONFIG_DEBUG_BFIN_HWTRACE_EXPAND
+ENTRY(_ex_trace_buff_full)
+        [--sp] = P3;
+        [--sp] = P2;
+        [--sp] = LC0;
+        [--sp] = LT0;
+        [--sp] = LB0;
+        P5.L = _trace_buff_offset;
+        P5.H = _trace_buff_offset;
+        P3 = [P5];              /* trace_buff_offset */
+        P5.L = lo(TBUFSTAT);
+        P5.H = hi(TBUFSTAT);
+        R7 = [P5];
+        R7 <<= 1;               /* double, since we need to read twice */
+        LC0 = R7;
+        R7 <<= 2;               /* need to shift over again,
+                                 * to get the number of bytes */
+        P5.L = lo(TBUF);
+        P5.H = hi(TBUF);
+        R6 = ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN)*1024) - 1;
+
+        P2 = R7;
+        P3 = P3 + P2;
+        R7 = P3;
+        R7 = R7 & R6;
+        P3 = R7;
+        P2.L = _trace_buff_offset;
+        P2.H = _trace_buff_offset;
+        [P2] = P3;
+
+        P2.L = _software_trace_buff;
+        P2.H = _software_trace_buff;
+
+        LSETUP (.Lstart, .Lend) LC0;
+.Lstart:
+        R7 = [P5];      /* read TBUF */
+        P4 = P3 + P2;
+        [P4] = R7;
+        P3 += -4;
+        R7 = P3;
+        R7 = R7 & R6;
+.Lend:
+        P3 = R7;
+
+        LB0 = [sp++];
+        LT0 = [sp++];
+        LC0 = [sp++];
+        P2 = [sp++];
+        P3 = [sp++];
+        jump _return_from_exception;
+
+#if CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN == 4
+.data
+#else
+.section .l1.data.B
+#endif
+ENTRY(_trace_buff_offset)
+        .long 0;
+ALIGN
+ENTRY(_software_trace_buff)
+        .rept ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN)*256);
+        .long 0
+        .endr
+#endif
+
 /*
  * Put these in the kernel data section - that should always be covered by
  * a CPLB. This is needed to ensure we don't get double fault conditions
@@ -764,7 +833,11 @@ _extable:
         .long _ex_trap_c        /* 0x0E - User Defined */
         .long _ex_trap_c        /* 0x0F - User Defined */
         .long _ex_single_step   /* 0x10 - HW Single step */
+#ifdef CONFIG_DEBUG_BFIN_HWTRACE_EXPAND
+        .long _ex_trace_buff_full /* 0x11 - Trace Buffer Full */
+#else
         .long _ex_trap_c        /* 0x11 - Trace Buffer Full */
+#endif
         .long _ex_trap_c        /* 0x12 - Reserved */
         .long _ex_trap_c        /* 0x13 - Reserved */
         .long _ex_trap_c        /* 0x14 - Reserved */