On 11/08/2012 01:01 PM, Stephen Warren wrote:
From: Stephen Warren <swarren@xxxxxxxxxx>
Currently, whenever CONFIG_ARCH_USES_GETTIMEOFFSET is enabled, each
arch core provides a single implementation of arch_gettimeoffset(). In
many cases, different sub-architectures, different machines, or
different timer providers exist, and so the arch ends up implementing
arch_gettimeoffset() as a call-through-pointer anyway. Examples are
ARM, Cris, M68K, and it's arguable that the remaining architectures,
M32R and Blackfin, should be doing this anyway.
Modify arch_gettimeoffset so that it itself is a function pointer, which
the arch initializes. This will allow later changes to move the
initialization of this function into individual machine support or timer
drivers. This is particularly useful for code in drivers/clocksource
which should rely on an arch-independant mechanism to register their
implementation of arch_gettimeoffset().
This patch also converts the Cris architecture to set arch_gettimeoffset
directly to the final implementation in time_init(), because Cris already
had separate time_init() functions per sub-architecture. M68K and ARM
are converted to set arch_gettimeoffset the final implementation in later
patches, because they already have function pointers in place for this
purpose.
[snip]
diff --git a/include/linux/time.h b/include/linux/time.h
index 4d358e9..05e32a7 100644
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -142,9 +142,7 @@ void timekeeping_inject_sleeptime(struct timespec *delta);
* finer then tick granular time.
*/
#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
-extern u32 arch_gettimeoffset(void);
-#else
-static inline u32 arch_gettimeoffset(void) { return 0; }
+extern u32 (*arch_gettimeoffset)(void);
#endif
extern void do_gettimeofday(struct timeval *tv);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index e424970..9d00ace 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -140,6 +140,20 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
}
/* Timekeeper helper functions. */
+
+#ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
+u32 (*arch_gettimeoffset)(void);
+
+u32 gettimeoffset(void)
+{
+ if (likely(arch_gettimeoffset))
+ return arch_gettimeoffset();
+ return 0;
+}
+#else
+static inline u32 gettimeoffset(void) { return 0; }
+#endif
Minor nit-pick here, but get_arch_timeoffset() or get_arch_tickoffset()
might be clearer, as gettimeoffset() sounds a little generic, and could
be confused with the higher-level timekeeping_inject_offset() call.
Otherwise this looks ok to me (disclaimer: I'm back from a 4 week leave,
so I may not have my brain plugged in all the way yet).
thanks
-john
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