sparc: Write to prom console using indirect buffer.

sparc64 systems have a restriction in that passing in buffer
addressses above 4GB to prom calls is not reliable.

We end up violating this when we do prom console writes, because we
use an on-stack buffer to translate '\n' into '\r\n'.

So instead, do this translation into an intermediate buffer, which is
in the kernel image and thus below 4GB, then pass that to the PROM
console write calls.

On the 32-bit side we don't have to deal with any of these issues, so
the new prom_console_write_buf() uses the existing prom_nbputchar()
implementation.  However we can now mark those routines static.

Since the 64-bit side completely uses new code we can delete the
putchar bits as they are now completely unused.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 27 insertions, 5 deletions

diff --git a/arch/sparc/prom/printf.c b/arch/sparc/prom/printf.c
index 24031971f806..d9682f06b3b0 100644
--- a/arch/sparc/prom/printf.c
+++ b/arch/sparc/prom/printf.c
@@ -15,23 +15,45 @@
 
 #include <linux/kernel.h>
 #include <linux/compiler.h>
+#include <linux/spinlock.h>
 
 #include <asm/openprom.h>
 #include <asm/oplib.h>
 
+#define CONSOLE_WRITE_BUF_SIZE  1024
+
 static char ppbuf[1024];
+static char console_write_buf[CONSOLE_WRITE_BUF_SIZE];
+static DEFINE_RAW_SPINLOCK(console_write_lock);
 
 void notrace prom_write(const char *buf, unsigned int n)
 {
+        unsigned int dest_len;
+        unsigned long flags;
+        char *dest;
+
+        dest = console_write_buf;
+        raw_spin_lock_irqsave(&console_write_lock, flags);
+
+        dest_len = 0;
         while (n-- != 0) {
-                char ch = *buf;
+                char ch = *buf++;
                 if (ch == '\n') {
-                        char tmp = '\r';
-                        prom_putchar(&tmp);
+                        *dest++ = '\r';
+                        dest_len++;
+                }
+                *dest++ = ch;
+                dest_len++;
+                if (dest_len >= CONSOLE_WRITE_BUF_SIZE - 1) {
+                        prom_console_write_buf(console_write_buf, dest_len);
+                        dest = console_write_buf;
+                        dest_len = 0;
                 }
-                prom_putchar(buf);
-                buf++;
         }
+        if (dest_len)
+                prom_console_write_buf(console_write_buf, dest_len);
+
+        raw_spin_unlock_irqrestore(&console_write_lock, flags);
 }
 
 void notrace prom_printf(const char *fmt, ...)