sandbox: Move pre-console buffer out of the way of tracing

[pandora-u-boot.git] / board / sandbox / README.sandbox

diff --git a/board/sandbox/README.sandbox b/board/sandbox/README.sandbox
index 9b09404..48c1e2b 100644 (file)
--- a/board/sandbox/README.sandbox
+++ b/board/sandbox/README.sandbox
@@ -392,6 +392,49 @@ state_setprop() which does this automatically and avoids running out of
 space. See existing code for examples.
 
 
+Debugging the init sequence
+---------------------------
+
+If you get a failure in the initcall sequence, like this:
+
+   initcall sequence 0000560775957c80 failed at call 0000000000048134 (err=-96)
+
+Then you use can use grep to see which init call failed, e.g.:
+
+   $ grep 0000000000048134 u-boot.map
+   stdio_add_devices
+
+Of course another option is to run it with a debugger such as gdb:
+
+   $ gdb u-boot
+   ...
+   (gdb) br initcall.h:41
+   Breakpoint 1 at 0x4db9d: initcall.h:41. (2 locations)
+
+Note that two locations are reported, since this function is used in both
+board_init_f() and board_init_r().
+
+   (gdb) r
+   Starting program: /tmp/b/sandbox/u-boot
+   [Thread debugging using libthread_db enabled]
+   Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
+
+   U-Boot 2018.09-00264-ge0c2ba9814-dirty (Sep 22 2018 - 12:21:46 -0600)
+
+   DRAM:  128 MiB
+   MMC:
+
+   Breakpoint 1, initcall_run_list (init_sequence=0x5555559619e0 <init_sequence_f>)
+       at /scratch/sglass/cosarm/src/third_party/u-boot/files/include/initcall.h:41
+   41                              printf("initcall sequence %p failed at call %p (err=%d)\n",
+   (gdb) print *init_fnc_ptr
+   $1 = (const init_fnc_t) 0x55555559c114 <stdio_add_devices>
+   (gdb)
+
+
+This approach can be used on normal boards as well as sandbox.
+
+
 Testing
 -------
 
@@ -434,6 +477,9 @@ that are mapped into that memory:
       0   CONFIG_SYS_FDT_LOAD_ADDR   Device tree
    e000   CONFIG_BLOBLIST_ADDR       Blob list
   10000   CONFIG_MALLOC_F_ADDR       Early memory allocation
+  f0000   CONFIG_PRE_CON_BUF_ADDR    Pre-console buffer
+ 100000   CONFIG_TRACE_EARLY_ADDR    Early trace buffer (if enabled)
+=
 
 
 --