[people/ms/u-boot.git] / doc / README.omap-reset-time

README on how reset time on OMAPs should be calculated

CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC:
Most OMAPs' provide a way to specify the time for
which the reset should be held low while the voltages
and Oscillator outputs stabilize.

This time is mostly board and PMIC dependent. Hence the
boards are expected to specify a pre-computed time
using the above option, (the details on how to compute
the value are given below) without which a default time
as specified by CONFIG_DEFAULT_OMAP_RESET_TIME_MAX_USEC
is used.

The value for CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC
can be computed using a summation of the below 3 parameters
-1- Time taken by the Osciallator to stop and restart
-2- PMIC OTP time
-3- Voltage ramp time, which can be derived using the
PMIC slew rate and value of voltage ramp needed.
Commit	Line	Data
0b1b60c7 LV	1	README on how reset time on OMAPs should be calculated
	2
	3	CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC:
	4	Most OMAPs' provide a way to specify the time for
	5	which the reset should be held low while the voltages
	6	and Oscillator outputs stabilize.
	7
	8	This time is mostly board and PMIC dependent. Hence the
	9	boards are expected to specify a pre-computed time
	10	using the above option, (the details on how to compute
	11	the value are given below) without which a default time
	12	as specified by CONFIG_DEFAULT_OMAP_RESET_TIME_MAX_USEC
	13	is used.
	14
	15	The value for CONFIG_OMAP_PLATFORM_RESET_TIME_MAX_USEC
	16	can be computed using a summation of the below 3 parameters
	17	-1- Time taken by the Osciallator to stop and restart
	18	-2- PMIC OTP time
	19	-3- Voltage ramp time, which can be derived using the
	20	PMIC slew rate and value of voltage ramp needed.