[PATCH 04/11] ARM: set arch_gettimeoffset directly
rmallon at gmail.com
Fri Nov 9 22:39:10 EST 2012
On 10/11/12 08:07, Stephen Warren wrote:
> On 11/08/2012 04:06 PM, Ryan Mallon wrote:
>> On 09/11/12 08:01, Stephen Warren wrote:
>>> remove ARM's struct sys_timer .offset function pointer, and instead
>>> directly set the arch_gettimeoffset function pointer when the timer
>>> driver is initialized. This requires multiplying all function results
>>> by 1000, since the removed arm_gettimeoffset() did this. Also,
>>> s/unsigned long/u32/ just to make the function prototypes exactly
>>> match that of arch_gettimeoffset.
>>> +static u32 ep93xx_gettimeoffset(void)
>>> + int offset;
>>> + offset = __raw_readl(EP93XX_TIMER4_VALUE_LOW) - last_jiffy_time;
>>> + /* Calculate (1000000 / 983040) * offset. */
>> This comment is now incorrect, it should say:
>> /* Calculate (1000000000 / 983040) * offset */
>> or perhaps to better explain what is being done:
>> * Timer 4 is based on a 983.04 kHz reference clock,
>> * so dividing by 983040 gives a milli-second value.
>> * Refactor the calculation to avoid overflow.
>>> + return (offset + (53 * offset / 3072)) * 1000;
> Thanks. I expanded on that slightly and went for:
> * Timer 4 is based on a 983.04 kHz reference clock,
> * so dividing by 983040 gives the fraction of a second,
> * so dividing by 0.983040 converts to uS.
> * Refactor the calculation to avoid overflow.
> * Finally, multiply by 1000 to give nS.
Looks good, thanks.
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