console: Implement pre-console buffer
Allow redirection of console output prior to console initialisation to a
temporary buffer.
To enable this functionality, the board (or arch) must define:
- CONFIG_PRE_CONSOLE_BUFFER - Enable pre-console buffer
- CONFIG_PRE_CON_BUF_ADDR - Base address of pre-console buffer
- CONFIG_PRE_CON_BUF_SZ - Size of pre-console buffer (in bytes)
The pre-console buffer will buffer the last CONFIG_PRE_CON_BUF_SZ bytes
Any earlier characters are silently dropped.
diff --git a/README b/README
index 91b6695..dfc7ada 100644
--- a/README
+++ b/README
@@ -619,6 +619,20 @@
must be defined, to setup the maximum idle timeout for
the SMC.
+- Pre-Console Buffer:
+ Prior to the console being initialised (i.e. serial UART
+ initialised etc) all console output is silently discarded.
+ Defining CONFIG_PRE_CONSOLE_BUFFER will cause U-Boot to
+ buffer any console messages prior to the console being
+ initialised to a buffer of size CONFIG_PRE_CON_BUF_SZ
+ bytes located at CONFIG_PRE_CON_BUF_ADDR. The buffer is
+ a circular buffer, so if more than CONFIG_PRE_CON_BUF_SZ
+ bytes are output before the console is initialised, the
+ earlier bytes are discarded.
+
+ 'Sane' compilers will generate smaller code if
+ CONFIG_PRE_CON_BUF_SZ is a power of 2
+
- Boot Delay: CONFIG_BOOTDELAY - in seconds
Delay before automatically booting the default image;
set to -1 to disable autoboot.