Nishanth Menon <menon.nisha...@gmail.com> 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 <khil...@deeprootsystems.com>
>> ---
>> 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()
>> + } 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.
Thanks,
Kevin
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