Re: [PATCH v4 0/4] PM / QoS: Restore DEV_PM_QOS_MIN/MAX_FREQUENCY

[Chanwoo Choi <cw00.choi@samsung.com>]

On 11/29/19 11:20 PM, Leonard Crestez wrote:
> On 2019-11-29 1:34 PM, Rafael J. Wysocki wrote:
>> On Tuesday, November 26, 2019 4:17:09 PM CET Leonard Crestez wrote:
>>> Support for frequency limits in dev_pm_qos was removed when cpufreq was
>>> switched to freq_qos, this series attempts to restore it by
>>> reimplementing on top of freq_qos.
>>>
>>> Discussion about removal is here:
>>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flinux-pm%2FVI1PR04MB7023DF47D046AEADB4E051EBEE680%40VI1PR04MB7023.eurprd04.prod.outlook.com%2FT%2F%23u&data=02%7C01%7Cleonard.crestez%40nxp.com%7C4531c54354d54442d71808d774c02866%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637106240968746397&sdata=LYIRtXYe8qPz1G%2F0ADYpPhbhviv1pkk7%2B%2BQ1dX1DQR8%3D&reserved=0
>>>
>>> The cpufreq core switched away because it needs contraints at the level
>>> of a "cpufreq_policy" which cover multiple cpus so dev_pm_qos coupling
>>> to struct device was not useful. Cpufreq could only use dev_pm_qos by
>>> implementing an additional layer of aggregation anyway.
>>>
>>> However in the devfreq subsystem scaling is always performed on a per-device
>>> basis so dev_pm_qos is a very good match. Support for dev_pm_qos in devfreq
>>> core is here (latest version, no dependencies outside this series):
>>>
>>> 	https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11252409%2F&data=02%7C01%7Cleonard.crestez%40nxp.com%7C4531c54354d54442d71808d774c02866%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637106240968746397&sdata=YodRx0IRVsjQXYA5X7UEosn%2FatO%2BWREfotwWrley2DQ%3D&reserved=0
>>>
>>> That series is RFC mostly because it needs these PM core patches.
>>> Earlier versions got entangled in some locking cleanups but those are
>>> not strictly necessary to get dev_pm_qos functionality.
>>>
>>> In theory if freq_qos is extended to handle conflicting min/max values then
>>> this sharing would be valuable. Right now freq_qos just ties two unrelated
>>> pm_qos aggregations for min and max freq.
>>>
>>> ---
>>> This is implemented by embeding a freq_qos_request inside dev_pm_qos_request:
>>> the data field was already an union in order to deal with flag requests.
>>>
>>> The internal freq_qos_apply is exported so that it can be called from
>>> dev_pm_qos apply_constraints.
>>>
>>> The dev_pm_qos_constraints_destroy function has no obvious equivalent in
>>> freq_qos and the whole approach of "removing requests" is somewhat dubios:
>>> request objects should be owned by consumers and the list of qos requests
>>> will most likely be empty when the target device is deleted. Series follows
>>> current pattern for dev_pm_qos.
>>>
>>> First two patches can be applied separately.
>>>
>>> Changes since v3:
>>> * Fix s/QOS/QoS in patch 2 title
>>> * Improves comments in kunit test
>>> * Fix assertions after freq_qos_remove_request
>>> * Remove (c) from NXP copyright header
>>> * Wrap long lines in qos.c to be under 80 chars. This fixes checkpatch but the
>>> rule is already broken by code in the files.
>>> * Collect reviews
>>> Link to v3: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11260627%2F&data=02%7C01%7Cleonard.crestez%40nxp.com%7C4531c54354d54442d71808d774c02866%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637106240968746397&sdata=e%2B5SGU%2Bx4UjxlY292ejMO1kDewc3MmFvCpf0SDB0K4U%3D&reserved=0
>>>
>>> Changes since v2:
>>> * #define PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE FREQ_QOS_MAX_DEFAULT_VALUE
>>> * #define FREQ_QOS_MAX_DEFAULT_VALUE S32_MAX (in new patch)
>>> * Add initial kunit test for freq_qos, validating the MAX_DEFAULT_VALUE found
>>> by Matthias and another recent fix. Testing this should be easier!
>>> Link to v2: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11250413%2F&data=02%7C01%7Cleonard.crestez%40nxp.com%7C4531c54354d54442d71808d774c02866%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637106240968746397&sdata=vyz%2FN2x7OZPCSx4Md8yQkOSjPtfNUvW6%2FHtG0bTG1xU%3D&reserved=0
>>>
>>> Changes since v1:
>>> * Don't rename or EXPORT_SYMBOL_GPL the freq_qos_apply function; just
>>> drop the static marker.
>>> Link to v1: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11212887%2F&data=02%7C01%7Cleonard.crestez%40nxp.com%7C4531c54354d54442d71808d774c02866%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637106240968746397&sdata=SjcSQmMRZu0z3ATWygBpD8mRToCZT%2FBgQ7U3IRpMUB0%3D&reserved=0
>>>
>>> Leonard Crestez (4):
>>>    PM / QoS: Initial kunit test
>>>    PM / QoS: Redefine FREQ_QOS_MAX_DEFAULT_VALUE to S32_MAX
>>>    PM / QoS: Reorder pm_qos/freq_qos/dev_pm_qos structs
>>>    PM / QoS: Restore DEV_PM_QOS_MIN/MAX_FREQUENCY
>>>
>>>   drivers/base/Kconfig          |   4 ++
>>>   drivers/base/power/Makefile   |   1 +
>>>   drivers/base/power/qos-test.c | 117 ++++++++++++++++++++++++++++++++++
>>>   drivers/base/power/qos.c      |  73 +++++++++++++++++++--
>>>   include/linux/pm_qos.h        |  86 ++++++++++++++-----------
>>>   kernel/power/qos.c            |   4 +-
>>>   6 files changed, 242 insertions(+), 43 deletions(-)
>>>   create mode 100644 drivers/base/power/qos-test.c
>>>
>>>
>>
>> I have applied the whole series as 5.5 material, but I have reordered the fix
>> (patch [2/4]) before the rest of it and marked it for -stable.
> 
> Thanks!
> 
> Devfreq maintainers, do you think the devfreq parts could be queued for 
> 5.5 as well? I'm not sure about the mechanics involved in this since 
> devfreq qos depends at build time on this dev_pm_qos series.
> 
> Latest version is here: https://patchwork.kernel.org/cover/11252415/

Hi Leonard,

I agree devfreq's pm-qos patch.
[1] https://patchwork.kernel.org/cover/11252415/

But, I think need to discuss about this series[2].
Acutally, I don't want to split out the device_register.
[2]https://patchwork.kernel.org/cover/11242865/

> 
> It's RFC because it didn't compile against unpatched linux-next but it's 
> otherwise a reduced version of a series that went through review and 
> testing.
> 
> --
> Regards,
> Leonard
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics