On Thu, 16 Jul 2009 17:14:07 -0700
john stultz <johnstul@xxxxxxxxxx> wrote:
> This patch converts alpha to use GENERIC_TIME via the arch_getoffset()
> infrastructure, reducing the amount of arch specific code we need to
> maintain.
>
> I suspect the alpha arch could even be further improved to provide and
> rpcc() based clocksource, but not having the hardware, I don't feel
> comfortable attempting the more complicated conversion (but I'd be glad
> to help if anyone else is interested).
>
> This patch applies on top of Linus' current -git tree (2.6.31-rc3).
>
> I've taken my best swing at converting this, but I'm not 100% confident
> I got it right. My cross-compiler is now too old, so I couldn't check if
> it builds. So any assistance from arch maintainers or testers to get
> this merged would be great.
>
It breaks the build:
cc1: warnings being treated as errors
arch/alpha/kernel/time.c: In function 'arch_gettimeoffset':
arch/alpha/kernel/time.c:413: warning: unused variable 'partial_tick'
arch/alpha/kernel/time.c:413: warning: unused variable 'delta_cycles'
make[1]: *** [arch/alpha/kernel/time.o] Error 1
u32 arch_gettimeoffset(void)
{
unsigned long delta_cycles, delta_usec, partial_tick;
#ifdef CONFIG_SMP
/* Until and unless we figure out how to get cpu cycle counters
in sync and keep them there, we can't use the rpcc tricks. */
delta_usec = 0;
#else
delta_cycles = rpcc() - state.last_time;
partial_tick = state.partial_tick;
/*
* usec = cycles * ticks_per_cycle * 2**48 * 1e6 / (2**48 * ticks)
* = cycles * (s_t_p_c) * 1e6 / (2**48 * ticks)
* = cycles * (s_t_p_c) * 15625 / (2**42 * ticks)
*
* which, given a 600MHz cycle and a 1024Hz tick, has a
* dynamic range of about 1.7e17, which is less than the
* 1.8e19 in an unsigned long, so we are safe from overflow.
*
* Round, but with .5 up always, since .5 to even is harder
* with no clear gain.
*/
delta_usec = (delta_cycles * state.scaled_ticks_per_cycle
+ partial_tick) * 15625;
delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
#endif
return delta_usec * 1000;
}
I converted the CONFIG_SMP=y case into a plain old `return 0;'. Which
means that we could turn the CONFIG_SMP=y case into a static inline,
really.
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
cc1: warnings being treated as errors
arch/alpha/kernel/time.c: In function 'arch_gettimeoffset':
arch/alpha/kernel/time.c:413: warning: unused variable 'partial_tick'
arch/alpha/kernel/time.c:413: warning: unused variable 'delta_cycles'
make[1]: *** [arch/alpha/kernel/time.o] Error 1
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: John Stultz <johnstul@xxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: john stultz <johnstul@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/alpha/kernel/time.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
--- a/arch/alpha/kernel/time.c~alpha-convert-to-use-arch_gettimeoffset-fix
+++ a/arch/alpha/kernel/time.c
@@ -410,13 +410,13 @@ time_init(void)
*/
u32 arch_gettimeoffset(void)
{
- unsigned long delta_cycles, delta_usec, partial_tick;
-
#ifdef CONFIG_SMP
/* Until and unless we figure out how to get cpu cycle counters
in sync and keep them there, we can't use the rpcc tricks. */
- delta_usec = 0;
+ return 0;
#else
+ unsigned long delta_cycles, delta_usec, partial_tick;
+
delta_cycles = rpcc() - state.last_time;
partial_tick = state.partial_tick;
/*
@@ -435,9 +435,8 @@ u32 arch_gettimeoffset(void)
delta_usec = (delta_cycles * state.scaled_ticks_per_cycle
+ partial_tick) * 15625;
delta_usec = ((delta_usec / ((1UL << (FIX_SHIFT-6-1)) * HZ)) + 1) / 2;
-#endif
-
return delta_usec * 1000;
+#endif
}
/*
_
--
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