Hi !
On Mon, 27 Jun 2005, Maciej W. Rozycki wrote:
> How about using these prom_printf()s to implement a real early printk()?
> You'd save yourself and perhaps others a lot of hassle.
Here's what helped me *a lot* when debugging. It's rather ugly, polluting
printk.c with platform/driver-(cross-)dependent hacks, but output is available
immediately on kernel startup, and on some machines you just can't do without
that ;)
(perhaps someone sometimes will create a clean implementation...)
--- kernel/printk.c Tue Apr 19 21:43:47 2005
+++ kernel/printk.c Mon Jun 13 22:13:09 2005
@@ -33,6 +33,7 @@
#include <linux/syscalls.h>
#include <asm/uaccess.h>
+#define early_log_by_prom_write 1
#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
@@ -403,12 +403,27 @@
}
}
+static void inline __call_prom_write(unsigned long start, unsigned long end)
+{
+ static int prom_write(const char *s, int n);
+ prom_write(&LOG_BUF(start), end - start);
+}
+
/*
* Write out chars from start to end - 1 inclusive
*/
static void _call_console_drivers(unsigned long start,
unsigned long end, int msg_log_level)
{
+ if (/*msg_log_level < console_loglevel &&*/ start != end) {
+ if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
+ /* wrapped write */
+ __call_prom_write(start & LOG_BUF_MASK, log_buf_len);
+ __call_prom_write(0, end & LOG_BUF_MASK);
+ } else {
+ __call_prom_write(start, end);
+ }
+ }
if (msg_log_level < console_loglevel &&
console_drivers && start != end) {
if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
@@ -892,6 +907,7 @@
* for us.
*/
spin_lock_irqsave(&logbuf_lock, flags);
+/*if(!early_log_by_prom_write)*/
con_start = log_start;
spin_unlock_irqrestore(&logbuf_lock, flags);
}
@@ -994,3 +1010,27 @@
printk_ratelimit_burst);
}
EXPORT_SYMBOL(printk_ratelimit);
+
+#include <asm/sgialib.h>
+static int prom_write(const char *s, int n)
+{
+#ifdef CONFIG_SGI_IP28
+ extern int ip22zilog_is_active(void);
+ extern int impactgfx_is_active(void);
+ if (n > 0 && early_log_by_prom_write)
+ if(!ip22zilog_is_active() && !impactgfx_is_active())
+ { unsigned long oldstate;
+ int i;
+ romvec = ROMVECTOR;
+ oldstate = ip2628_enable_ucmem();
+ for (i = 0; i < n; ++i, ++s)
+ { if ('\n' == *s)
+ prom_putchar('\r');
+ prom_putchar(*s);
+ }
+ ip2628_return_ucmem(oldstate);
+ return 1;
+ }
+#endif
+ return 0;
+}
kind regards
pf
