[PATCH] ARM: TWD: fix the clock calculation for TWD
From: Russell King - ARM Linux <hidden>
Date: 2011-01-20 14:08:11
On Thu, Jan 20, 2011 at 02:33:57PM +0800, Chao Xie wrote:
quoted hunk ↗ jump to hunk
The original code will do count * (HZ /5). It will make the twd timer rate decreased if HZ can not be excatly divided. For example HZ=128. Signed-off-by: Chao Xie <redacted> --- arch/arm/kernel/smp_twd.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c index 35882fb..ca6405b 100644 --- a/arch/arm/kernel/smp_twd.c +++ b/arch/arm/kernel/smp_twd.c@@ -111,7 +111,8 @@ static void __cpuinit twd_calibrate_rate(void) count = __raw_readl(twd_base + TWD_TIMER_COUNTER); - twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5); + twd_timer_rate = ((unsigned long)(0xFFFFFFFFU - count)) + * HZ / 5; printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000, (twd_timer_rate / 100000) % 100);
I don't think this patch has any effect what so ever, so I just tried:
#define HZ 128
unsigned long twd_timer_rate;
void calc1(unsigned long count)
{
twd_timer_rate = (0xffffffffU - count) * (HZ / 5);
}
void calc2(unsigned long count)
{
twd_timer_rate = ((unsigned long)(0xffffffffU - count)) * (HZ / 5);
}
calc1:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
mvn r0, r0
add r0, r0, r0, asl #2
ldr r3, .L2
add r0, r0, r0, asl #2
@ lr needed for prologue
str r0, [r3, #0]
mov pc, lr
calc2:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
mvn r0, r0
add r0, r0, r0, asl #2
ldr r3, .L5
add r0, r0, r0, asl #2
@ lr needed for prologue
str r0, [r3, #0]
mov pc, lr
The code looks identical to me, so the patch appears to have no effect.