Kevin Hilman had written, on 01/11/2010 06:50 PM, the following:
Nishanth Menon <menon.nishanth@xxxxxxxxx> writes:
Kevin Hilman said the following on 01/08/2010 05:26 PM:
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@xxxxxxxxxxxxxxxxxxx>
---
arch/arm/plat-omap/include/plat/omap_device.h | 4 ++
arch/arm/plat-omap/omap_device.c | 41 ++++++++++++++++++++-----
2 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/arch/arm/plat-omap/include/plat/omap_device.h b/arch/arm/plat-omap/include/plat/omap_device.h
index dc1fac1..76d4917 100644
--- a/arch/arm/plat-omap/include/plat/omap_device.h
+++ b/arch/arm/plat-omap/include/plat/omap_device.h
@@ -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)
diff --git a/arch/arm/plat-omap/omap_device.c b/arch/arm/plat-omap/omap_device.c
index 1e5648d..d8c75c8 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);
nitpicky dumb comment: since the flags say auto adjust, do you care to
make this just a pr_info instead of a warning. it is not the same
severity as latency>activate_latency without AUTO_ADJUST right?
Agreed, will change to pr_info()
Thanks.
+ } 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);
nitpick: I think you need {} for the else part too now a days..
you mean as a CodingStyle issue, or a compiler issue?
do you have a reference for this requirement?
do you mean if the 'if' part has {}, the else part should too, even if
it's a single line?
I don't really care one way or the other, just want to know more about
what you're suggesting.
Apologies on the obscure comment. I meant Coding style.
Documentation/CodingStyle says:
171 This does not apply if one branch of a conditional statement is a
single
172 statement. Use braces in both branches.
173
174 if (condition) {
175 do_this();
176 do_that();
177 } else {
178 otherwise();
179 }
--
Regards,
Nishanth Menon
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