Blackfin: catch hardware errors earlier during booting

Allow hardware errors to be caught during early portions of booting, and
leave something in the shadow console that people can use to debug their
system with (to be printed out by the bootloader on next reset).

This enables the hardare error interrupts in head.S, allowing us to find
hardware errors when they happen (well, as much as you can with a hardware
error) and prints out the trace if it is enabled.  This will catch errors
(like booting the wrong image on a 533) which previously resulted in a
infinite loop/hang, as well as random hardware errors before before
setup_arch().

To disable this debug only feature - turn off EARLY_PRINTK.

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 70 insertions, 4 deletions

diff --git a/arch/blackfin/kernel/early_printk.c b/arch/blackfin/kernel/early_printk.c
index 2ab56811841c..931c78b5ea1f 100644
--- a/arch/blackfin/kernel/early_printk.c
+++ b/arch/blackfin/kernel/early_printk.c
@@ -27,6 +27,7 @@
 #include <linux/serial_core.h>
 #include <linux/console.h>
 #include <linux/string.h>
+#include <linux/reboot.h>
 #include <asm/blackfin.h>
 #include <asm/irq_handler.h>
 #include <asm/early_printk.h>
@@ -181,6 +182,22 @@ asmlinkage void __init init_early_exception_vectors(void)
         u32 evt;
         SSYNC();
 
+        /*
+         * This starts up the shadow buffer, incase anything crashes before
+         * setup arch
+         */
+        mark_shadow_error();
+        early_shadow_puts(linux_banner);
+        early_shadow_stamp();
+
+        if (CPUID != bfin_cpuid()) {
+                early_shadow_puts("Running on wrong machine type, expected");
+                early_shadow_reg(CPUID, 16);
+                early_shadow_puts(", but running on");
+                early_shadow_reg(bfin_cpuid(), 16);
+                early_shadow_puts("\n");
+        }
+
         /* cannot program in software:
          * evt0 - emulation (jtag)
          * evt1 - reset
@@ -199,6 +216,7 @@ asmlinkage void __init init_early_exception_vectors(void)
 
 }
 
+__attribute__((__noreturn__))
 asmlinkage void __init early_trap_c(struct pt_regs *fp, void *retaddr)
 {
         /* This can happen before the uart is initialized, so initialize
@@ -210,10 +228,58 @@ asmlinkage void __init early_trap_c(struct pt_regs *fp, void *retaddr)
         if (likely(early_console == NULL) && CPUID == bfin_cpuid())
                 setup_early_printk(DEFAULT_EARLY_PORT);
 
-        printk(KERN_EMERG "Early panic\n");
-        dump_bfin_mem(fp);
-        show_regs(fp);
-        dump_bfin_trace_buffer();
+        if (!shadow_console_enabled()) {
+                /* crap - we crashed before setup_arch() */
+                early_shadow_puts("panic before setup_arch\n");
+                early_shadow_puts("IPEND:");
+                early_shadow_reg(fp->ipend, 16);
+                if (fp->seqstat & SEQSTAT_EXCAUSE) {
+                        early_shadow_puts("\nEXCAUSE:");
+                        early_shadow_reg(fp->seqstat & SEQSTAT_EXCAUSE, 8);
+                }
+                if (fp->seqstat & SEQSTAT_HWERRCAUSE) {
+                        early_shadow_puts("\nHWERRCAUSE:");
+                        early_shadow_reg(
+                                (fp->seqstat & SEQSTAT_HWERRCAUSE) >> 14, 8);
+                }
+                early_shadow_puts("\nErr @");
+                if (fp->ipend & EVT_EVX)
+                        early_shadow_reg(fp->retx, 32);
+                else
+                        early_shadow_reg(fp->pc, 32);
+#ifdef CONFIG_DEBUG_BFIN_HWTRACE_ON
+                early_shadow_puts("\nTrace:");
+                if (likely(bfin_read_TBUFSTAT() & TBUFCNT)) {
+                        while (bfin_read_TBUFSTAT() & TBUFCNT) {
+                                early_shadow_puts("\nT  :");
+                                early_shadow_reg(bfin_read_TBUF(), 32);
+                                early_shadow_puts("\n S :");
+                                early_shadow_reg(bfin_read_TBUF(), 32);
+                        }
+                }
+#endif
+                early_shadow_puts("\nUse bfin-elf-addr2line to determine "
+                        "function names\n");
+                /*
+                 * We should panic(), but we can't - since panic calls printk,
+                 * and printk uses memcpy.
+                 * we want to reboot, but if the machine type is different,
+                 * can't due to machine specific reboot sequences
+                 */
+                if (CPUID == bfin_cpuid()) {
+                        early_shadow_puts("Trying to restart\n");
+                        machine_restart("");
+                }
+
+                early_shadow_puts("Halting, since it is not safe to restart\n");
+                while (1)
+                        asm volatile ("EMUEXCPT; IDLE;\n");
+
+        } else {
+                printk(KERN_EMERG "Early panic\n");
+                show_regs(fp);
+                dump_bfin_trace_buffer();
+        }
 
         panic("Died early");
 }