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author | Paul Mackerras <paulus@samba.org> | 2007-10-31 22:25:35 +1100 |
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committer | Paul Mackerras <paulus@samba.org> | 2007-11-08 14:15:31 +1100 |
commit | 43875cc0a54d936132010e58545269e183741fae (patch) | |
tree | 65409e7b9161fcaf8a88b67ebe91ffdb2ad97809 /include/asm-powerpc | |
parent | 465ccab9eb8209a2a402710b24a9bff127b25b94 (diff) | |
download | linux-43875cc0a54d936132010e58545269e183741fae.tar.gz linux-43875cc0a54d936132010e58545269e183741fae.tar.bz2 linux-43875cc0a54d936132010e58545269e183741fae.zip |
[POWERPC] Fix off-by-one error in setting decrementer on Book E/4xx (v2)
The decrementer in Book E and 4xx processors interrupts on the
transition from 1 to 0, rather than on the 0 to -1 transition as on
64-bit server and 32-bit "classic" (6xx/7xx/7xxx) processors. At the
moment we subtract 1 from the count of how many decrementer ticks are
required before the next interrupt before putting it into the
decrementer, which is correct for server/classic processors, but could
possibly cause the interrupt to happen too early on Book E and 4xx if
the timebase/decrementer frequency is low.
This fixes the problem by making set_dec subtract 1 from the count for
server and classic processors, instead of having the callers subtract
1. Since set_dec already had a bunch of ifdefs to handle different
processor types, there is no net increase in ugliness. :)
Note that calling set_dec(0) may not generate an interrupt on some
processors. To make sure that decrementer_set_next_event always calls
set_dec with an interval of at least 1 tick, we set min_delta_ns of
the decrementer_clockevent to correspond to 2 ticks (2 rather than 1
to compensate for truncations in the conversions between ticks and
ns).
This also removes a redundant call to set the decrementer to
0x7fffffff - it was already set to that earlier in timer_interrupt.
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'include/asm-powerpc')
-rw-r--r-- | include/asm-powerpc/time.h | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/include/asm-powerpc/time.h b/include/asm-powerpc/time.h index f05895522f7f..780f82642756 100644 --- a/include/asm-powerpc/time.h +++ b/include/asm-powerpc/time.h @@ -176,25 +176,31 @@ static inline unsigned int get_dec(void) #endif } +/* + * Note: Book E and 4xx processors differ from other PowerPC processors + * in when the decrementer generates its interrupt: on the 1 to 0 + * transition for Book E/4xx, but on the 0 to -1 transition for others. + */ static inline void set_dec(int val) { #if defined(CONFIG_40x) mtspr(SPRN_PIT, val); #elif defined(CONFIG_8xx_CPU6) - set_dec_cpu6(val); + set_dec_cpu6(val - 1); #else +#ifndef CONFIG_BOOKE + --val; +#endif #ifdef CONFIG_PPC_ISERIES - int cur_dec; - if (firmware_has_feature(FW_FEATURE_ISERIES) && get_lppaca()->shared_proc) { get_lppaca()->virtual_decr = val; - cur_dec = get_dec(); - if (cur_dec > val) + if (get_dec() > val) HvCall_setVirtualDecr(); - } else + return; + } #endif - mtspr(SPRN_DEC, val); + mtspr(SPRN_DEC, val); #endif /* not 40x or 8xx_CPU6 */ } |