Linux-PM Archive on lore.kernel.org
 help / color / Atom feed
From: Leonard Crestez <leonard.crestez@nxp.com>
To: Matthias Kaehlcke <mka@chromium.org>,
	MyungJoo Ham <myungjoo.ham@samsung.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>
Cc: "Chanwoo Choi" <cw00.choi@samsung.com>,
	"Kyungmin Park" <kyungmin.park@samsung.com>,
	"Artur Świgoń" <a.swigon@partner.samsung.com>,
	"Saravana Kannan" <saravanak@google.com>,
	"Krzysztof Kozlowski" <krzk@kernel.org>,
	"Alexandre Bailon" <abailon@baylibre.com>,
	"Georgi Djakov" <georgi.djakov@linaro.org>,
	"Abel Vesa" <abel.vesa@nxp.com>, "Jacky Bai" <ping.bai@nxp.com>,
	"Viresh Kumar" <viresh.kumar@linaro.org>,
	"Lukasz Luba" <l.luba@partner.samsung.com>,
	dl-linux-imx <linux-imx@nxp.com>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v9 0/8] PM / devfreq: Add dev_pm_qos support
Date: Wed, 23 Oct 2019 14:06:40 +0000
Message-ID: <AM7PR04MB70154D3BA0D6402A9C9BE6A0EE6B0@AM7PR04MB7015.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <cover.1570044052.git.leonard.crestez@nxp.com>

On 2019-10-02 10:25 PM, Leonard Crestez wrote:
> Add dev_pm_qos notifiers to devfreq core in order to support frequency
> limits via dev_pm_qos_add_request.
> 
> Unlike the rest of devfreq the dev_pm_qos frequency is measured in Khz,
> this is consistent with current dev_pm_qos usage for cpufreq and
> allows frequencies above 2Ghz (pm_qos expresses limits as s32).
> 
> Like with cpufreq the handling of min_freq/max_freq is moved to the
> dev_pm_qos mechanism. Constraints from userspace are no longer clamped on
> store, instead all values can be written and we only check against OPPs in a
> new devfreq_get_freq_range function. This is consistent with the design of
> dev_pm_qos.
> 
> Notifiers from pm_qos are executed under a single global dev_pm_qos_mtx and
> need to take devfreq->lock. Notifier registration takes the same dev_pm_qos_mtx
> so in order to prevent lockdep warnings it must be done outside devfreq->lock.
> Current devfreq_add_device does all initialization under devfreq->lock and that
> needs to be relaxed.
> 
> Some of first patches in the series are bugfixes and cleanups, they could be
> applied separately.

Hello,

This series was posted a few ago and all patches have been 
reviewed/tested-by multiple people. Possible minor hangups:

1) Matthias found it confusing that min/max_freq in sysfs changes 
on-the-fly. This is not a behavior change and I believe a decent 
workaround would be to implement separate user_min/max_freq files from 
which userspace will always read back the contraints it has written.

2) There was an objection to removing devm from two allocs in PATCH 4. I 
believe current solution is acceptable but a possible alternative would 
be to split device_register into device_initialize and device_add: this 
should allow devm sooner.
Link: https://patchwork.kernel.org/patch/11158385/#22902151

Let me know if you think I should implement the options above and resend.

The bigger problem is that DEV_PM_QOS_MIN/MAX_FREQUENCY was removed from 
pm core because only user (cpufreq) was refactored to use a new 
interface on top of cpufreq_policy. Links to discussion:
     https://patchwork.kernel.org/cover/11193021/
 
https://lore.kernel.org/linux-pm/VI1PR04MB7023DF47D046AEADB4E051EBEE680@VI1PR04MB7023.eurprd04.prod.outlook.com/T/#u

I believe there is still significant value in supporting min/max 
frequency requests on a per-target-device basis. This makes much more 
sense for devfreq that for cpufreq because the whole point of devfreq is 
scaling arbitrary independent devices.

> ---
> Changes since v8:
> * Fix incorrectly reading qos max twice in get_freq_range.
> * Make devfreq_notifier_call set scaling_max_freq to ULONG_MAX instead of 0 on
> error. This avoids special-casing this in get_freq_range.
> * Add a fix for devfreq_notifier_call returning -errno.
> * Replace S32_MAX with PM_QOS_MAX_FREQUENCY_DEFAULT_VALUE. This seems cleaner
> and avoids overflow when multiplying S32_MAX with 1000 on 32bit platforms. It
> overflowed to 0xfffffc18 hz so it was mostly safe anyway.
> * Warn when encountering errors on cleanup (but continue).
> * Incorporate other smaller comment and printk adjustments from review.
> Link to v8:
> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11158383%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=YKKW1RJl1YArhtjlA859DeRxys4d4iiB%2FQIz3Nl8OtU%3D&amp;reserved=0
> 
> Changes since v7:
> * Only #define HZ_PER_KHZ in patch where it's used.
> * Drop devfreq_ prefix for some internal functions.
> * Improve qos update error message.
> * Remove some unnecessary comments.
> * Collect reviews
> Link to v7: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11157649%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=0s6mH192c3dvDlfrFEVdqdMqoFRM4QJiLZiRg4c89nQ%3D&amp;reserved=0
> 
> Changes since v6:
> * Don't return errno from devfreq_qos_notifier_call, return NOTIFY_DONE
> and print the error.
> * More spelling and punctuation nits
> Link to v6: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11157201%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=6hcaCgESymHhCk5UbFC182FrgFVdJdDoorAJhZXKuTg%3D&amp;reserved=0
> 
> Changes since v5:
> * Drop patches which are not strictly related to PM QoS.
> * Add a comment explaining why devfreq_add_device needs two cleanup paths.
> * Remove {} for single line.
> * Rename {min,max}_freq_req to user_{min,max}_freq_req
> * Collect reviews
> Link to v5: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11149497%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=oDuaTI7bpOlCEs9mFRgY5eUvGX%2FtpP6m0U5t4SYNKaw%3D&amp;reserved=0
> 
> Changes since v4:
> * Move more devfreq_add_device init ahead of device_register.
> * Make devfreq_dev_release cleanup devices not yet in devfreq_list. This is
> simpler than previous attempt to add to devfreq_list sonner.
> * Take devfreq->lock in trans_stat_show
> * Register dev_pm_opp notifier on devfreq parent dev (which has OPPs)
> Link to v4: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11114657%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=ItIVLxJZVOpO2XL2MBqONWLQ1lHFu2gA7GC1yb%2BQgEE%3D&amp;reserved=0
> 
> Changes since v3:
> * Cleanup locking and error-handling in devfreq_add_device
> * Register notifiers after device registration but before governor start
> * Keep the initialization of min_req/max_req ahead of device_register
> because it's used for sysfs handling
> * Use HZ_PER_KHZ instead of 1000
> * Add kernel-doc comments
> * Move OPP notifier to core
> Link to v3: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fcover%2F11104061%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=unedjnBbjVtifB8koQ0B8eOjqwCnnAeqHGI8QYuH%2Fv4%3D&amp;reserved=0
> 
> Changes since v2:
> * Handle sysfs via dev_pm_qos (in separate patch)
> * Add locking to {min,max}_freq_show
> * Fix checkpatch issues (long lines etc)
> Link to v2: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F11084279%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=boHOmdwyUhKlmk7F3X8oYbLq1MvR4dQWlF14I0AXXes%3D&amp;reserved=0
> 
> Changes since v1:
> * Add doxygen comments for min_nb/max_nb
> * Remove notifiers on error/cleanup paths. Keep gotos simple by relying on
> dev_pm_qos_remove_notifier ignoring notifiers which were not added.
> Link to v1: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F11078475%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Ca6b53046361642d0fd5708d7476e40e4%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637056411174276846&amp;sdata=DZlQAKLqQc4Q46a7v%2FtEBexsp1jDSLB8yuZcLXPEHl4%3D&amp;reserved=0
> 
> Leonard Crestez (8):
>    PM / devfreq: Don't fail devfreq_dev_release if not in list
>    PM / devfreq: Fix devfreq_notifier_call returning errno
>    PM / devfreq: Set scaling_max_freq to max on OPP notifier error
>    PM / devfreq: Move more initialization before registration
>    PM / devfreq: Don't take lock in devfreq_add_device
>    PM / devfreq: Introduce get_freq_range helper
>    PM / devfreq: Add PM QoS support
>    PM / devfreq: Use PM QoS for sysfs min/max_freq
> 
>   drivers/devfreq/devfreq.c | 310 ++++++++++++++++++++++++++------------
>   include/linux/devfreq.h   |  14 +-
>   2 files changed, 224 insertions(+), 100 deletions(-)
> 


  parent reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-02 19:25 Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 1/8] PM / devfreq: Don't fail devfreq_dev_release if not in list Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 2/8] PM / devfreq: Fix devfreq_notifier_call returning errno Leonard Crestez
2019-10-02 21:24   ` Matthias Kaehlcke
2019-10-02 23:47     ` Leonard Crestez
2019-10-31  2:29   ` Chanwoo Choi
2019-10-02 19:25 ` [PATCH v9 3/8] PM / devfreq: Set scaling_max_freq to max on OPP notifier error Leonard Crestez
2019-10-02 21:33   ` Matthias Kaehlcke
2019-10-31  2:21   ` Chanwoo Choi
2019-10-02 19:25 ` [PATCH v9 4/8] PM / devfreq: Move more initialization before registration Leonard Crestez
2019-10-31  3:15   ` Chanwoo Choi
2019-10-31 13:31     ` Leonard Crestez
2019-11-01  8:31       ` Chanwoo Choi
2019-11-01 14:36         ` Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 5/8] PM / devfreq: Don't take lock in devfreq_add_device Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 6/8] PM / devfreq: Introduce get_freq_range helper Leonard Crestez
2019-10-03 18:19   ` Matthias Kaehlcke
2019-10-03 19:16     ` Leonard Crestez
2019-10-03 19:36       ` Matthias Kaehlcke
2019-10-11 18:29     ` Matthias Kaehlcke
2019-10-31  2:44       ` Chanwoo Choi
2019-10-31  2:42   ` Chanwoo Choi
2019-10-31 13:12     ` Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 7/8] PM / devfreq: Add PM QoS support Leonard Crestez
2019-10-02 22:22   ` Matthias Kaehlcke
2019-10-04 17:04   ` Matthias Kaehlcke
2019-10-31  3:01   ` Chanwoo Choi
2019-10-31 13:21     ` Leonard Crestez
2019-10-02 19:25 ` [PATCH v9 8/8] PM / devfreq: Use PM QoS for sysfs min/max_freq Leonard Crestez
2019-10-04 17:05   ` Matthias Kaehlcke
2019-10-31  3:10   ` Chanwoo Choi
2019-10-23 14:06 ` Leonard Crestez [this message]
2019-10-23 16:34   ` [PATCH v9 0/8] PM / devfreq: Add dev_pm_qos support Matthias Kaehlcke
2019-10-24 16:21     ` Leonard Crestez

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=AM7PR04MB70154D3BA0D6402A9C9BE6A0EE6B0@AM7PR04MB7015.eurprd04.prod.outlook.com \
    --to=leonard.crestez@nxp.com \
    --cc=a.swigon@partner.samsung.com \
    --cc=abailon@baylibre.com \
    --cc=abel.vesa@nxp.com \
    --cc=cw00.choi@samsung.com \
    --cc=georgi.djakov@linaro.org \
    --cc=krzk@kernel.org \
    --cc=kyungmin.park@samsung.com \
    --cc=l.luba@partner.samsung.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-imx@nxp.com \
    --cc=linux-pm@vger.kernel.org \
    --cc=mka@chromium.org \
    --cc=myungjoo.ham@samsung.com \
    --cc=ping.bai@nxp.com \
    --cc=rafael@kernel.org \
    --cc=saravanak@google.com \
    --cc=viresh.kumar@linaro.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-PM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-pm/0 linux-pm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-pm linux-pm/ https://lore.kernel.org/linux-pm \
		linux-pm@vger.kernel.org
	public-inbox-index linux-pm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-pm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git