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.
*/
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