Peter Marheine has uploaded this change for review.

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Make sleep threshold for delays configurable

This allows the minimum time that default_delay() will choose to sleep
for instead of polling to be configured at build-time. The default
remains unchanged at 100 milliseconds for now.

Change-Id: Ida96e0816ac914ed69d6fd82ad90ebe89cdef1cc
Signed-off-by: Peter Marheine <pmarheine@chromium.org>
---
M Makefile
M meson.build
M meson_options.txt
M udelay.c
M udelay_dos.c
5 files changed, 15 insertions(+), 8 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/06/81606/1

diff --git a/Makefile b/Makefile
index f8aa136..09b31b3 100644
--- a/Makefile
+++ b/Makefile
@@ -542,6 +542,8 @@
 # Disable wiki printing by default. It is only useful if you have wiki access.
 CONFIG_PRINT_WIKI ?= no
 
+CONFIG_DELAY_MINIMUM_SLEEP_US ?= 100000
+
 # Disable all features if CONFIG_NOTHING=yes is given unless CONFIG_EVERYTHING was also set
 ifeq ($(CONFIG_NOTHING), yes)
   ifeq ($(CONFIG_EVERYTHING), yes)
@@ -587,6 +589,7 @@
 endif
 
 FEATURE_FLAGS += -D'CONFIG_DEFAULT_PROGRAMMER_ARGS="$(CONFIG_DEFAULT_PROGRAMMER_ARGS)"'
+FEATURE_FLAGS += -D'CONFIG_DELAY_MINIMUM_SLEEP_US=$(CONFIG_DELAY_MINIMUM_SLEEP_US)'
 
 ################################################################################
 
diff --git a/meson.build b/meson.build
index 1c8316e..d4a5b9c 100644
--- a/meson.build
+++ b/meson.build
@@ -112,6 +112,9 @@
   delay_src = files('udelay_dos.c')
 endif
 srcs += delay_src
+cargs += ['-DCONFIG_DELAY_MINIMUM_SLEEP_US=@0@'.format(
+  get_option('delay_minimum_sleep_us')
+)]
 
 # check for required symbols
 if cc.has_function('clock_gettime')
diff --git a/meson_options.txt b/meson_options.txt
index e62deb6..8a04114 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -22,3 +22,6 @@
 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,
+       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.')
diff --git a/udelay.c b/udelay.c
index 14900c7..85ed5b3 100644
--- a/udelay.c
+++ b/udelay.c
@@ -96,11 +96,10 @@
 /* Precise delay. */
 void default_delay(unsigned int usecs)
 {
-	/* If the delay is >0.1 s, use internal_sleep because timing does not need to be so precise. */
-	if (usecs > 100000) {
-		internal_sleep(usecs);
-	} else {
+	if (usecs < CONFIG_DELAY_MINIMUM_SLEEP_US) {
 		clock_usec_delay(usecs);
+	} else {
+		internal_sleep(usecs);
 	}
 }
 
diff --git a/udelay_dos.c b/udelay_dos.c
index 4a29f73..21ca9b8 100644
--- a/udelay_dos.c
+++ b/udelay_dos.c
@@ -158,14 +158,13 @@
 {
 	static bool calibrated = false;
 
-	/* If the delay is >0.1 s, use internal_sleep because timing does not need to be so precise. */
-	if (usecs > 100000) {
-		internal_sleep(usecs);
-	} else {
+	if (usecs < CONFIG_DELAY_MINIMUM_SLEEP_US) {
 		if (!calibrated) {
 			myusec_calibrate_delay();
 			calibrated = true;
 		}
 		myusec_delay(usecs);
+	} else {
+		internal_sleep(usecs);
 	}
 }

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