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diff --git a/Documentation/mips/time.README b/Documentation/mips/time.README deleted file mode 100644 index 70bc0dd43d6..00000000000 --- a/Documentation/mips/time.README +++ /dev/null @@ -1,198 +0,0 @@ -README for MIPS time services - -Jun Sun -jsun@mvista.com or jsun@junsun.net - - -ABOUT ------ -This file describes the new arch/mips/kernel/time.c, related files and the -services they provide. - -If you are short in patience and just want to know how to use time.c for a -new board or convert an existing board, go to the last section. - - -FILES, COMPATABILITY AND CONFIGS ---------------------------------- - -The old arch/mips/kernel/time.c is renamed to old-time.c. - -A new time.c is put there, together with include/asm-mips/time.h. - -Two configs variables are introduced, CONFIG_OLD_TIME_C and CONFIG_NEW_TIME_C. -So we allow boards using - - 1) old time.c (CONFIG_OLD_TIME_C) - 2) new time.c (CONFIG_NEW_TIME_C) - 3) neither (their own private time.c) - -However, it is expected every board will move to the new time.c in the near -future. - - -WHAT THE NEW CODE PROVIDES? ---------------------------- - -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 - dispatched in assemably code (usually int-handler.S) - - -WHAT THE NEW CODE REQUIRES? ---------------------------- - -For the new code to work properly, each board implementation needs to supply -the following functions or values: - - a) board_time_init - a function pointer. Invoked at the beginnig of - time_init(). It is optional. - 1. (optional) set up RTC routines - 2. (optional) calibrate and set the mips_counter_frequency - - b) board_timer_setup - a function pointer. Invoked at the end of time_init() - 1. (optional) over-ride any decisions made in time_init() - 2. set up the irqaction for timer interrupt. - 3. enable the timer interrupt - - c) (optional) board-specific RTC routines. - - d) (optional) mips_counter_frequency - It must be definied if the board - is using CPU counter for timer interrupt or it is using fixed rate - gettimeoffset(). - - -PORTING GUIDE -------------- - -Step 1: decide how you like to implement the time services. - - a) does this board have a RTC? If yes, implement the two RTC funcs. - - b) does the CPU have counter/compare registers? - - 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? - - In order to use CPU counter register as the timer interrupt source, you - must know the counter speed (mips_counter_frequency). It is usually the - same as the CPU speed or an integral divisor of it. - - d) decide on whether you want to use high-level or low-level timer - interrupt routines. The low-level one is presumably faster, but should - not make too mcuh difference. - - -Step 2: the machine setup() function - - If you supply board_time_init(), set the function poointer. - - Set the function pointer board_timer_setup() (mandatory) - - -Step 3: implement rtc routines, board_time_init() and board_timer_setup() - if needed. - - board_time_init() - - a) (optional) set up RTC routines, - b) (optional) calibrate and set the mips_counter_frequency - (only needed if you intended to use fixed_rate_gettimeoffset - or use cpu counter as timer interrupt source) - - board_timer_setup() - - a) (optional) over-write any choices made above by time_init(). - b) machine specific code should setup the timer irqaction. - c) enable the timer interrupt - - - If the RTC chip is a common chip, I suggest the routines are put under - arch/mips/libs. For example, for DS1386 chip, one would create - rtc-ds1386.c under arch/mips/lib directory. Add the following line to - the arch/mips/lib/Makefile: - - obj-$(CONFIG_DDB5476) += rtc-ds1386.o - -Step 4: if you are using low-level timer interrupt, change your interrupt - dispathcing code to check for timer interrupt and jump to - ll_timer_interrupt() directly if one is detected. - -Step 5: Modify arch/mips/config.in and add CONFIG_NEW_TIME_C to your machine. - Modify the appropriate defconfig if applicable. - -Final notes: - -For some tricky cases, you may need to add your own wrapper functions -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). - - -PORTING NOTES FOR SMP ----------------------- - -If you have a SMP box, things are slightly more complicated. - -The time service running every jiffy is logically divided into two parts: - - 1) the one for the whole system (defined in timer_interrupt()) - 2) the one that should run for each CPU (defined in local_timer_interrupt()) - -You need to decide on your timer interrupt sources. - - case 1) - whole system has only one timer interrupt delivered to one CPU - - In this case, you set up timer interrupt as in UP systems. In addtion, - you need to set emulate_local_timer_interrupt to 1 so that other - CPUs get to call local_timer_interrupt(). - - THIS IS CURRENTLY NOT IMPLEMNETED. However, it is rather easy to write - one should such a need arise. You simply make a IPI call. - - case 2) - each CPU has a separate timer interrupt - - In this case, you need to set up IRQ such that each of them will - call local_timer_interrupt(). In addition, you need to arrange - one and only one of them to call timer_interrupt(). - - 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. |