[PATCH] Fix IXP4xx CLOCK_TICK_RATE

Deepak Saxena · Linus Torvalds · commit 9138dccbb9f3 · 2005-08-23T20:06:33.000-07:00
As pointed out in the following thread, the CLOCK_TICK_RATE setting for IXP4xx is incorrect b/c the HW ignores the lowest 2 bits of the LATCH value. http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2005-August/030950.html Tnx to George Anziger and Egil Hjelmeland for finding the issue. Signed-off-by: Deepak Saxena <dsaxena@plexity.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/asm-arm/arch-ixp4xx/timex.h b/include/asm-arm/arch-ixp4xx/timex.h
@@ -7,7 +7,9 @@
 
 /*
  * We use IXP425 General purpose timer for our timer needs, it runs at 
- * 66.66... MHz
+ * 66.66... MHz. We do a convulted calculation of CLOCK_TICK_RATE b/c the
+ * timer register ignores the bottom 2 bits of the LATCH value.
  */
-#define CLOCK_TICK_RATE (66666666)
+#define FREQ 66666666
+#define CLOCK_TICK_RATE (((FREQ / HZ & ~IXP4XX_OST_RELOAD_MASK) + 1) * HZ)
 
