From 75a23850cd282eeafbe23d6a9ade4eaf23babd51 Mon Sep 17 00:00:00 2001
From: Finn Thain <fthain@telegraphics.com.au>
Date: Mon, 18 Jul 2011 00:06:10 +1000
Subject: [PATCH] m68k/mac: Fix compiler warning in via_read_time()
The algorithm described in the comment compares two reads from the RTC but
the code actually reads once and compares the result to an uninitialized
value. This causes the compiler to warn, "last_result maybe used
uninitialized". Make the code match the comment, fix the warning and
perhaps improve reliability. Tested on a Quadra 700.
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
arch/m68k/mac/misc.c | 40 +++++++++++++++++++++++-----------------
1 file changed, 23 insertions(+), 17 deletions(-)
diff --git a/arch/m68k/mac/misc.c b/arch/m68k/mac/misc.c
index e023fc6b37e5..eb915551de69 100644
--- a/arch/m68k/mac/misc.c
+++ b/arch/m68k/mac/misc.c
@@ -304,35 +304,41 @@ static void via_write_pram(int offset, __u8 data)
static long via_read_time(void)
{
union {
- __u8 cdata[4];
- long idata;
+ __u8 cdata[4];
+ long idata;
} result, last_result;
- int ct;
+ int count = 1;
+
+ via_pram_command(0x81, &last_result.cdata[3]);
+ via_pram_command(0x85, &last_result.cdata[2]);
+ via_pram_command(0x89, &last_result.cdata[1]);
+ via_pram_command(0x8D, &last_result.cdata[0]);
/*
* The NetBSD guys say to loop until you get the same reading
* twice in a row.
*/
- ct = 0;
- do {
- if (++ct > 10) {
- printk("via_read_time: couldn't get valid time, "
- "last read = 0x%08lx and 0x%08lx\n",
- last_result.idata, result.idata);
- break;
- }
-
- last_result.idata = result.idata;
- result.idata = 0;
-
+ while (1) {
via_pram_command(0x81, &result.cdata[3]);
via_pram_command(0x85, &result.cdata[2]);
via_pram_command(0x89, &result.cdata[1]);
via_pram_command(0x8D, &result.cdata[0]);
- } while (result.idata != last_result.idata);
- return result.idata - RTC_OFFSET;
+ if (result.idata == last_result.idata)
+ return result.idata - RTC_OFFSET;
+
+ if (++count > 10)
+ break;
+
+ last_result.idata = result.idata;
+ }
+
+ pr_err("via_read_time: failed to read a stable value; "
+ "got 0x%08lx then 0x%08lx\n",
+ last_result.idata, result.idata);
+
+ return 0;
}
/*
--
2.20.1