reduce DELAY_MINIMUM_SLEEP_US to 100 by default

This makes flashrom sleep more eagerly rather than busy-waiting,
observing that most delays in flashrom are either less than 100
microseconds (barely enough time to get any work done, even on a fast
machine) or much more than 1 millisecond (very wasteful to busy-loop).
Since we believe most systems offer good timer resolution that should
provide sleep latency on the order of 100 microseconds, this is a
reasonable default.

For DOS, the default is set to 50ms because the best available timing
source on DOS only ticks at about 20 Hz.

Signed-off-by: Peter Marheine <pmarheine@chromium.org>
Change-Id: I0f431d240c670446218b14811ef62a34e4c83da2
Reviewed-on: https://review.coreboot.org/c/flashrom/+/81608
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Anastasia Klimchuk <aklm@chromium.org>

meson_cross/i586_djgpp_dos.txt

@@ -30,6 +30,8 @@ default_library = 'static'
 [project options]
 tests = 'disabled'
 ich_descriptors_tool = 'disabled'
+# DOS time resolution is only about 50ms
+delay_minimum_sleep_us = 50000
 
 [properties]
 sys_root = '/usr/local/djgpp'

meson_options.txt

@@ -21,6 +21,6 @@ option('man-pages', type : 'feature', value : 'auto', description : 'build the m
 option('documentation', type : 'feature', value : 'auto', description : 'build the html documentation')
 option('ni845x_search_path', type : 'string', value : 'C:\Program Files (x86)\National Instruments\Ni-845x\MS Visual C',
        description : 'Path to search for the proprietary ni845x library and header (32-bit Windows only)')
-option('delay_minimum_sleep_us', type : 'integer', min : 0, value : 100000,
+option('delay_minimum_sleep_us', type : 'integer', min : 0, value : 100,
        description : 'Minimum time in microseconds to suspend execution for (rather than polling) when a delay is required.'
                    + ' Larger values may perform better on machines with low timer resolution, at the cost of increased power.')