On 11/08/2012 04:06 PM, Ryan Mallon wrote:

On 09/11/12 08:01, Stephen Warren wrote:

quoted

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.

quoted

+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.
	 */

quoted

+	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.
	 */