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

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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>
This commit is contained in:
Kevin Hilman 2010-01-26 20:13:02 -07:00 committed by Paul Walmsley
parent f0271d65f9
commit 9799aca203
2 changed files with 37 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
arch/arm/plat-omap/include/plat/omap_device.h
View file

@ -131,11 +131,15 @@ int omap_device_enable_clocks(struct omap_device *od);
*/
struct omap_device_pm_latency {
u32 deactivate_lat;
u32 deactivate_lat_worst;
int (*deactivate_func)(struct omap_device *od);
u32 activate_lat;
u32 activate_lat_worst;
int (*activate_func)(struct omap_device *od);
u32 flags;
};
#define OMAP_DEVICE_LATENCY_AUTO_ADJUST BIT(1)
/* Get omap_device pointer from platform_device pointer */
#define to_omap_device(x) container_of((x), struct omap_device, pdev)

41
arch/arm/plat-omap/omap_device.c
View file

@ -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;