diff options
Diffstat (limited to 'Documentation/mips')
| -rw-r--r-- | Documentation/mips/time.README | 39 |
1 files changed, 8 insertions, 31 deletions
diff --git a/Documentation/mips/time.README b/Documentation/mips/time.README index e1304b6..a4ce603 100644 --- a/Documentation/mips/time.README +++ b/Documentation/mips/time.README @@ -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. |