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[MIPS] Fixup migration to GENERIC_TIME

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Since we already moved to GENERIC_TIME, we should implement alternatives
of old do_gettimeoffset routines to get sub-jiffies resolution from
gettimeofday().  This patch includes:

 * MIPS clocksource support (based on works by Manish Lachwani).
 * remove unused gettimeoffset routines and related codes.
 * remove unised 64bit do_div64_32().
 * simplify mips_hpt_init. (no argument needed, __init tag)
 * simplify c0_hpt_timer_init. (no need to write to c0_count)
 * remove some hpt_init routines.
 * mips_hpt_mask variable to specify bitmask of hpt value.
 * convert jmr3927_do_gettimeoffset to jmr3927_hpt_read.
 * convert ip27_do_gettimeoffset to ip27_hpt_read.
 * convert bcm1480_do_gettimeoffset to bcm1480_hpt_read.
 * simplify sb1250 hpt functions. (no need to subtract and shift)
    
Signed-off-by: Atsushi Nemoto <[email protected]>
Signed-off-by: Ralf Baechle <[email protected]>
This commit is contained in:
Atsushi Nemoto 2006-10-24 00:21:27 +09:00 • committed by Ralf Baechle
commit 16b7b2ac01
13 changed files with 103 additions and 522 deletions
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39
Documentation/mips/time.README
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@ -38,19 +38,14 @@ The new time code provide the following services:
a) Implements functions required by Linux common code:
time_init
do_gettimeofday
do_settimeofday
b) provides an abstraction of RTC and null RTC implementation as default.
extern unsigned long (*rtc_get_time)(void);
extern int (*rtc_set_time)(unsigned long);
c) a set of gettimeoffset functions for different CPUs and different
needs.
d) high-level and low-level timer interrupt routines where the timer
interrupt source may or may not be the CPU timer. The high-level
routine is dispatched through do_IRQ() while the low-level is
c) high-level and low-level timer interrupt routines where the timer
interrupt source may or may not be the CPU timer. The high-level
routine is dispatched through do_IRQ() while the low-level is
dispatched in assemably code (usually int-handler.S)
@ -73,8 +68,7 @@ the following functions or values:
c) (optional) board-specific RTC routines.
d) (optional) mips_hpt_frequency - It must be definied if the board
is using CPU counter for timer interrupt or it is using fixed rate
gettimeoffset().
is using CPU counter for timer interrupt.
PORTING GUIDE
@ -89,16 +83,6 @@ Step 1: decide how you like to implement the time services.
If the answer is no, you need a timer to provide the timer interrupt
at 100 HZ speed.
You cannot use the fast gettimeoffset functions, i.e.,
unsigned long fixed_rate_gettimeoffset(void);
unsigned long calibrate_div32_gettimeoffset(void);
unsigned long calibrate_div64_gettimeoffset(void);
You can use null_gettimeoffset() will gives the same time resolution as
jiffy. Or you can implement your own gettimeoffset (probably based on
some ad hoc hardware on your machine.)
c) The following sub steps assume your CPU has counter register.
Do you plan to use the CPU counter register as the timer interrupt
or use an exnternal timer?
@ -123,8 +107,8 @@ Step 3: implement rtc routines, board_time_init() and plat_timer_setup()
board_time_init() -
a) (optional) set up RTC routines,
b) (optional) calibrate and set the mips_hpt_frequency
(only needed if you intended to use fixed_rate_gettimeoffset
or use cpu counter as timer interrupt source)
(only needed if you intended to use cpu counter as timer interrupt
source)
plat_timer_setup() -
a) (optional) over-write any choices made above by time_init().
@ -154,8 +138,8 @@ for some of the functions in time.c.
For example, you may define your own timer interrupt routine, which does
some of its own processing and then calls timer_interrupt().
You can also over-ride any of the built-in functions (gettimeoffset,
RTC routines and/or timer interrupt routine).
You can also over-ride any of the built-in functions (RTC routines
and/or timer interrupt routine).
PORTING NOTES FOR SMP
@ -187,10 +171,3 @@ You need to decide on your timer interrupt sources.
You can also do the low-level version of those interrupt routines,
following similar dispatching routes described above.
Note about do_gettimeoffset():
It is very likely the CPU counter registers are not sync'ed up in a SMP box.
Therefore you cannot really use the many of the existing routines that
are based on CPU counter. You should wirte your own gettimeoffset rouinte
if you want intra-jiffy resolution.