mirror of
https://github.com/adulau/aha.git
synced 2024-12-27 19:26:25 +00:00
[MIPS] Delete totally outdated Documentation/mips/time.README
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Ralf Baechle
parent
1d9ef3ecd7
commit
6f75aaa72a
2 changed files with 0 additions and 175 deletions
|
|
@ -4,5 +4,3 @@ AU1xxx_IDE.README
|
|||
- README for MIPS AU1XXX IDE driver.
|
||||
GT64120.README
|
||||
- README for dir with info on MIPS boards using GT-64120 or GT-64120A.
|
||||
time.README
|
||||
- README for MIPS time services.
|
||||
|
|
|
|||
|
|
@ -1,173 +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
|
||||
|
||||
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) 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_hpt_frequency
|
||||
|
||||
b) plat_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_hpt_frequency - It must be definied if the board
|
||||
is using CPU counter for timer interrupt.
|
||||
|
||||
|
||||
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.
|
||||
|
||||
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_hpt_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.
|
||||
|
||||
|
||||
Step 3: implement rtc routines, board_time_init() and plat_timer_setup()
|
||||
if needed.
|
||||
|
||||
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 cpu counter as timer interrupt
|
||||
source)
|
||||
|
||||
plat_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 (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.
|
||||
Loading…
Reference in a new issue