OMAP: omap_device: optionally auto-adjust device activate/deactivate latencies

First, this patch adds new worst-case latency values to the
omap_device_pm_latency struct.  Here the worst-case measured latencies
for the activate and deactivate hooks are stored.

In addition, add an option to auto-adjust the latency values used for
device activate/deactivate.

By setting a new 'OMAP_DEVICE_LATENCY_AUTO_ADJUST' flag in the
omap_device_pm_latency struct, the omap_device layer automatically
adjusts the activate/deactivate latencies to the worst-case measured
values.

Anytime a new worst-case value is found, it is printed to the console.
Here is an example log during boot using UART2 s an example.  After
boot, the OPP is manually changed to the 125MHz OPP:

[...]
Freeing init memory: 128K
omap_device: serial8250.2: new worst case deactivate latency 0: 30517
omap_device: serial8250.2: new worst case activate latency 0: 30517
omap_device: serial8250.2: new worst case activate latency 0: 218139648
omap_device: serial8250.2: new worst case deactivate latency 0: 61035
omap_device: serial8250.2: new worst case activate latency 0: 278076171
omap_device: serial8250.2: new worst case activate latency 0: 298614501
omap_device: serial8250.2: new worst case activate latency 0: 327331542

/ # echo 125000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed

omap_device: serial8250.2: new worst case deactivate latency 0: 91552

Motivation: this can be used as a technique to automatically determine
the worst case latency values.  The current method of printing a
warning on every violation is too noisy to actually interact the
console in order to set low OPP to discover latencies.

Another motivation for this patch is that the activate/deactivate
latenices can vary depending on the idlemode of the device.  While
working on the UARTs, I noticed that when using no-idle, the activate
latencies were as high as several hundred msecs as shown above.  When
the UARTs are in smart-idle, the max latency is well under 100 usecs.

Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>

1 files changed, 33 insertions, 8 deletions

diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
index 1e5648d3e3d8..d8c75c8f78d7 100644
--- a/arch/arm/plat-omap/omap_device.c
+++ b/arch/arm/plat-omap/omap_device.c
@@ -148,10 +148,22 @@ static int _omap_device_activate(struct omap_device *od, u8 ignore_lat)
 			 "%llu nsec\n", od->pdev.name, od->pm_lat_level,
 			 act_lat);
 
-		WARN(act_lat > odpl->activate_lat, "omap_device: %s.%d: "
-		     "activate step %d took longer than expected (%llu > %d)\n",
-		     od->pdev.name, od->pdev.id, od->pm_lat_level,
-		     act_lat, odpl->activate_lat);
+		if (act_lat > odpl->activate_lat) {
+			odpl->activate_lat_worst = act_lat;
+			if (odpl->flags & OMAP_DEVICE_LATENCY_AUTO_ADJUST) {
+				odpl->activate_lat = act_lat;
+				pr_warning("omap_device: %s.%d: new worst case "
+					   "activate latency %d: %llu\n",
+					   od->pdev.name, od->pdev.id,
+					   od->pm_lat_level, act_lat);
+			} else
+				pr_warning("omap_device: %s.%d: activate "
+					   "latency %d higher than exptected. "
+					   "(%llu > %d)\n",
+					   od->pdev.name, od->pdev.id,
+					   od->pm_lat_level, act_lat,
+					   odpl->activate_lat);
+		}
 
 		od->dev_wakeup_lat -= odpl->activate_lat;
 	}
@@ -204,10 +216,23 @@ static int _omap_device_deactivate(struct omap_device *od, u8 ignore_lat)
 			 "%llu nsec\n", od->pdev.name, od->pm_lat_level,
 			 deact_lat);
 
-		WARN(deact_lat > odpl->deactivate_lat, "omap_device: %s.%d: "
-		     "deactivate step %d took longer than expected "
-		     "(%llu > %d)\n", od->pdev.name, od->pdev.id,
-		     od->pm_lat_level, deact_lat, odpl->deactivate_lat);
+		if (deact_lat > odpl->deactivate_lat) {
+			odpl->deactivate_lat_worst = deact_lat;
+			if (odpl->flags & OMAP_DEVICE_LATENCY_AUTO_ADJUST) {
+				odpl->deactivate_lat = deact_lat;
+				pr_warning("omap_device: %s.%d: new worst case "
+					   "deactivate latency %d: %llu\n",
+					   od->pdev.name, od->pdev.id,
+					   od->pm_lat_level, deact_lat);
+			} else
+				pr_warning("omap_device: %s.%d: deactivate "
+					   "latency %d higher than exptected. "
+					   "(%llu > %d)\n",
+					   od->pdev.name, od->pdev.id,
+					   od->pm_lat_level, deact_lat,
+					   odpl->deactivate_lat);
+		}
+
 
 		od->dev_wakeup_lat += odpl->activate_lat;