This patch fixes several issues with the SP804 delay timer on FVP:
* By default, the SP804 dual timer on FVP runs at 32 KHz. In order
to run the timer at 35 MHz (as specified in the FVP user manual)
the Overwrite bit in the SP810 control register must be set.
* The CLKMULT and CLKDIV definitions are mixed up:
delta(us) = delta(ticks) * T(us) = delta(ticks) / f(MHz)
From the delay function:
delta_us = (delta * ops->clk_mult) / ops->clk_div;
Matching both expressions:
1 / f(MHz) = ops->clk_mult / ops->clk_div
And consequently:
f(MHz) = ops->clk_div / ops->clk_mult
Which, for a 35 MHz timer, translates to:
ops->clk_div = 35
ops->clk_mult = 1
* The comment in the delay timer header file has been corrected:
The ratio of the multiplier and the divider is the clock period
in microseconds, not the frequency.
Change-Id: Iffd5ce0a5a28fa47c0720c0336d81b678ff8fdf1
The API is simple. The BSP or specific timer driver creates an
instance of timer_ops_t, fills in the timer specific data, then calls
timer_init(). The timer specific data includes a function pointer
to return the timer value and a clock multiplier/divider. The ratio
of the multiplier and the divider is the clock frequency in MHz.
After that, mdelay() or udelay() can be called to delay execution for
the specified time (milliseconds or microseconds, respectively).
Change-Id: Icf8a295e1d25874f789bf28b7412156329dc975c
Co-authored-by: Dan Handley <dan.handley@arm.com>
Juan Castillo
Ryan Harkin