From: thierry.reding@gmail.com (Thierry Reding)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH 00/15] pwm: add support for atomic update
Date: Mon, 20 Jul 2015 09:43:41 +0200 [thread overview]
Message-ID: <20150720074339.GA29614@ulmo> (raw)
In-Reply-To: <1435738921-25027-1-git-send-email-boris.brezillon@free-electrons.com>
On Wed, Jul 01, 2015 at 10:21:46AM +0200, Boris Brezillon wrote:
> Hello Thierry,
>
> This series adds support for atomic PWM update, or ITO, the capability
> to update all the parameters of a PWM device (enabled/disabled, period,
> duty and polarity) in one go.
>
> This implementation is still experimental, and I may have missed some key
> aspect, so any feedback are welcome.
>
> Also note that I haven't protected the state update with any locking.
> That's because the existing config does not protect against concurrent
> access to a requested PWM device (see the pwm_config implementation).
> I guess the PWM framework assume the user will implement the proper locking
> scheme if it has to concurrently access the device.
Actually the reason why no protection is needed is because there can
ever only be a single user of a PWM channel. pwm_request() will only
hand out a handle to the PWM channel if it hasn't been requested
before.
And in the unlikely case where a single user wants to use the same PWM
channel from different threads, then it will have to use locking for
other reasons already, so accesses to the PWM can be serialized using
the same mechanism.
Thierry
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WARNING: multiple messages have this Message-ID (diff)
From: Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Boris Brezillon
<boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
Cc: linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Liam Girdwood <lgirdwood-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Bryan Wu <cooloney-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Richard Purdie <rpurdie-Fm38FmjxZ/leoWH0uzbU5w@public.gmane.org>,
Jacek Anaszewski
<j.anaszewski-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
linux-leds-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
Jean-Christophe Plagniol-Villard
<plagnioj-sclMFOaUSTBWk0Htik3J/w@public.gmane.org>,
Tomi Valkeinen <tomi.valkeinen-l0cyMroinI0@public.gmane.org>,
linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>,
Alexandre Courbot
<gnurou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Maxime Ripard
<maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>,
Jingoo Han <jingoohan1-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
Doug Anderson <dianders-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC PATCH 00/15] pwm: add support for atomic update
Date: Mon, 20 Jul 2015 09:43:41 +0200 [thread overview]
Message-ID: <20150720074339.GA29614@ulmo> (raw)
In-Reply-To: <1435738921-25027-1-git-send-email-boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
[-- Attachment #1: Type: text/plain, Size: 1213 bytes --]
On Wed, Jul 01, 2015 at 10:21:46AM +0200, Boris Brezillon wrote:
> Hello Thierry,
>
> This series adds support for atomic PWM update, or ITO, the capability
> to update all the parameters of a PWM device (enabled/disabled, period,
> duty and polarity) in one go.
>
> This implementation is still experimental, and I may have missed some key
> aspect, so any feedback are welcome.
>
> Also note that I haven't protected the state update with any locking.
> That's because the existing config does not protect against concurrent
> access to a requested PWM device (see the pwm_config implementation).
> I guess the PWM framework assume the user will implement the proper locking
> scheme if it has to concurrently access the device.
Actually the reason why no protection is needed is because there can
ever only be a single user of a PWM channel. pwm_request() will only
hand out a handle to the PWM channel if it hasn't been requested
before.
And in the unlikely case where a single user wants to use the same PWM
channel from different threads, then it will have to use locking for
other reasons already, so accesses to the PWM can be serialized using
the same mechanism.
Thierry
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: Thierry Reding <thierry.reding@gmail.com>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 00/15] pwm: add support for atomic update
Date: Mon, 20 Jul 2015 07:43:41 +0000 [thread overview]
Message-ID: <20150720074339.GA29614@ulmo> (raw)
In-Reply-To: <1435738921-25027-1-git-send-email-boris.brezillon@free-electrons.com>
[-- Attachment #1: Type: text/plain, Size: 1213 bytes --]
On Wed, Jul 01, 2015 at 10:21:46AM +0200, Boris Brezillon wrote:
> Hello Thierry,
>
> This series adds support for atomic PWM update, or ITO, the capability
> to update all the parameters of a PWM device (enabled/disabled, period,
> duty and polarity) in one go.
>
> This implementation is still experimental, and I may have missed some key
> aspect, so any feedback are welcome.
>
> Also note that I haven't protected the state update with any locking.
> That's because the existing config does not protect against concurrent
> access to a requested PWM device (see the pwm_config implementation).
> I guess the PWM framework assume the user will implement the proper locking
> scheme if it has to concurrently access the device.
Actually the reason why no protection is needed is because there can
ever only be a single user of a PWM channel. pwm_request() will only
hand out a handle to the PWM channel if it hasn't been requested
before.
And in the unlikely case where a single user wants to use the same PWM
channel from different threads, then it will have to use locking for
other reasons already, so accesses to the PWM can be serialized using
the same mechanism.
Thierry
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 819 bytes --]
next prev parent reply other threads:[~2015-07-20 7:43 UTC|newest]
Thread overview: 204+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-01 8:21 [RFC PATCH 00/15] pwm: add support for atomic update Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` [RFC PATCH 01/15] pwm: add the pwm_is_enabled() helper Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 7:47 ` Thierry Reding
2015-07-20 7:47 ` Thierry Reding
2015-07-20 7:47 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 02/15] pwm: fix pwm_get_period and pwm_get_duty_cycle prototypes Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 7:50 ` Thierry Reding
2015-07-20 7:50 ` Thierry Reding
2015-07-20 7:50 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 03/15] pwm: add pwm_get_polarity helper function Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 7:52 ` Thierry Reding
2015-07-20 7:52 ` Thierry Reding
2015-07-20 7:52 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 04/15] pwm: make use of pwm_get_xxx helpers where appropriate Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 8:00 ` Thierry Reding
2015-07-20 8:00 ` Thierry Reding
2015-07-20 8:00 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 05/15] pwm: introduce default period and polarity concepts Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-02 6:44 ` Uwe Kleine-König
2015-07-02 6:44 ` Uwe Kleine-König
2015-07-02 6:44 ` Uwe Kleine-König
2015-07-02 7:49 ` Boris Brezillon
2015-07-02 7:49 ` Boris Brezillon
2015-07-02 7:49 ` Boris Brezillon
2015-07-20 8:03 ` Thierry Reding
2015-07-20 8:03 ` Thierry Reding
2015-07-20 8:03 ` Thierry Reding
2015-07-20 8:14 ` Boris Brezillon
2015-07-20 8:14 ` Boris Brezillon
2015-07-20 8:14 ` Boris Brezillon
2015-07-20 8:22 ` Thierry Reding
2015-07-20 8:22 ` Thierry Reding
2015-07-20 8:22 ` Thierry Reding
2015-07-20 8:32 ` Boris Brezillon
2015-07-20 8:32 ` Boris Brezillon
2015-07-20 8:32 ` Boris Brezillon
2015-07-01 8:21 ` [RFC PATCH 06/15] pwm: define a new pwm_state struct Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 8:04 ` Thierry Reding
2015-07-20 8:04 ` Thierry Reding
2015-07-20 8:04 ` Thierry Reding
2015-07-20 10:01 ` Boris Brezillon
2015-07-20 10:01 ` Boris Brezillon
2015-07-20 10:01 ` Boris Brezillon
2015-07-20 10:09 ` Thierry Reding
2015-07-20 10:09 ` Thierry Reding
2015-07-20 10:09 ` Thierry Reding
2015-07-20 10:12 ` Boris Brezillon
2015-07-20 10:12 ` Boris Brezillon
2015-07-20 10:12 ` Boris Brezillon
2015-07-01 8:21 ` [RFC PATCH 07/15] pwm: move the enabled/disabled info to " Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 8:11 ` Thierry Reding
2015-07-20 8:11 ` Thierry Reding
2015-07-20 8:11 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 08/15] backlight: pwm_bl: remove useless call to pwm_set_period Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 8:16 ` Thierry Reding
2015-07-20 8:16 ` Thierry Reding
2015-07-20 8:16 ` Thierry Reding
2015-07-20 8:21 ` Boris Brezillon
2015-07-20 8:21 ` Boris Brezillon
2015-07-20 8:21 ` Boris Brezillon
2015-07-20 8:36 ` Thierry Reding
2015-07-20 8:36 ` Thierry Reding
2015-07-20 8:36 ` Thierry Reding
2015-07-20 8:50 ` Boris Brezillon
2015-07-20 8:50 ` Boris Brezillon
2015-07-20 8:50 ` Boris Brezillon
2015-07-20 9:10 ` Thierry Reding
2015-07-20 9:10 ` Thierry Reding
2015-07-20 9:10 ` Thierry Reding
2015-07-20 9:57 ` Boris Brezillon
2015-07-20 9:57 ` Boris Brezillon
2015-07-20 9:57 ` Boris Brezillon
2015-07-20 10:01 ` Thierry Reding
2015-07-20 10:01 ` Thierry Reding
2015-07-20 10:01 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 09/15] pwm: declare a default PWM state Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` [RFC PATCH 10/15] pwm: add the PWM initial state retrieval infra Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 9:01 ` Thierry Reding
2015-07-20 9:01 ` Thierry Reding
2015-07-20 9:01 ` Thierry Reding
2015-07-20 9:42 ` Boris Brezillon
2015-07-20 9:42 ` Boris Brezillon
2015-07-20 9:42 ` Boris Brezillon
2015-07-01 8:21 ` [RFC PATCH 11/15] pwm: add the core infrastructure to allow atomic update Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-20 8:59 ` Thierry Reding
2015-07-20 8:59 ` Thierry Reding
2015-07-20 8:59 ` Thierry Reding
2015-07-20 9:48 ` Boris Brezillon
2015-07-20 9:48 ` Boris Brezillon
2015-07-20 9:48 ` Boris Brezillon
2015-07-20 10:04 ` Thierry Reding
2015-07-20 10:04 ` Thierry Reding
2015-07-20 10:04 ` Thierry Reding
2015-07-01 8:21 ` [RFC PATCH 12/15] pwm: rockchip: add initial state retrieval Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 21:44 ` Heiko Stübner
2015-07-01 21:44 ` Heiko Stübner
2015-07-01 21:44 ` Heiko Stübner
2015-07-02 7:46 ` Boris Brezillon
2015-07-02 7:46 ` Boris Brezillon
2015-07-02 7:46 ` Boris Brezillon
2015-07-01 8:21 ` [RFC PATCH 13/15] pwm: rockchip: add support for atomic update Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 8:21 ` Boris Brezillon
2015-07-01 21:48 ` Heiko Stübner
2015-07-01 21:48 ` Heiko Stübner
2015-07-01 21:48 ` Heiko Stübner
2015-07-02 7:43 ` Boris Brezillon
2015-07-02 7:43 ` Boris Brezillon
2015-07-02 7:43 ` Boris Brezillon
2015-07-01 8:22 ` [RFC PATCH 14/15] regulator: pwm: implement ->enable(), ->disable() and ->is_enabled methods Boris Brezillon
2015-07-01 8:22 ` Boris Brezillon
2015-07-01 8:22 ` Boris Brezillon
2015-07-01 11:58 ` Heiko Stübner
2015-07-01 11:58 ` Heiko Stübner
2015-07-01 11:58 ` Heiko Stübner
2015-07-01 12:05 ` Boris Brezillon
2015-07-01 12:05 ` Boris Brezillon
2015-07-01 12:05 ` Boris Brezillon
2015-07-01 12:08 ` Heiko Stübner
2015-07-01 12:08 ` Heiko Stübner
2015-07-01 12:08 ` Heiko Stübner
2015-07-01 12:19 ` Boris Brezillon
2015-07-01 12:19 ` Boris Brezillon
2015-07-01 12:19 ` Boris Brezillon
2015-07-14 10:50 ` Mark Brown
2015-07-14 10:50 ` Mark Brown
2015-07-14 10:50 ` Mark Brown
2015-07-14 11:02 ` Boris Brezillon
2015-07-14 11:02 ` Boris Brezillon
2015-07-14 11:02 ` Boris Brezillon
2015-07-14 11:08 ` Mark Brown
2015-07-14 11:08 ` Mark Brown
2015-07-14 11:08 ` Mark Brown
2015-07-14 11:16 ` Boris Brezillon
2015-07-14 11:16 ` Boris Brezillon
2015-07-14 11:16 ` Boris Brezillon
2015-07-01 8:22 ` [RFC PATCH 15/15] regulator: pwm: properly initialize the ->state field Boris Brezillon
2015-07-01 8:22 ` Boris Brezillon
2015-07-01 8:22 ` Boris Brezillon
2015-07-14 10:51 ` Mark Brown
2015-07-14 10:51 ` Mark Brown
2015-07-14 10:51 ` Mark Brown
2015-07-14 11:03 ` Boris Brezillon
2015-07-14 11:03 ` Boris Brezillon
2015-07-14 11:03 ` Boris Brezillon
2015-07-01 21:50 ` [RFC PATCH 16/15] pwm: add informations about polarity, duty cycle and period to debugfs Heiko Stübner
2015-07-01 21:50 ` Heiko Stübner
2015-07-01 21:50 ` Heiko Stübner
2015-07-02 13:01 ` Boris Brezillon
2015-07-02 13:01 ` Boris Brezillon
2015-07-02 13:01 ` Boris Brezillon
2015-07-03 8:43 ` [PATCH] " Heiko Stübner
2015-07-03 8:43 ` Heiko Stübner
2015-07-03 8:43 ` Heiko Stübner
2015-07-01 21:57 ` [RFC PATCH 00/15] pwm: add support for atomic update Heiko Stübner
2015-07-01 21:57 ` Heiko Stübner
2015-07-01 21:57 ` Heiko Stübner
2015-07-02 7:55 ` Boris Brezillon
2015-07-02 7:55 ` Boris Brezillon
2015-07-02 7:55 ` Boris Brezillon
2015-07-02 7:03 ` Uwe Kleine-König
2015-07-02 7:03 ` Uwe Kleine-König
2015-07-02 7:03 ` Uwe Kleine-König
2015-07-02 7:17 ` Tomi Valkeinen
2015-07-02 7:17 ` Tomi Valkeinen
2015-07-02 7:17 ` Tomi Valkeinen
2015-07-02 7:42 ` Uwe Kleine-König
2015-07-02 7:42 ` Uwe Kleine-König
2015-07-02 7:42 ` Uwe Kleine-König
2015-07-02 7:30 ` Boris Brezillon
2015-07-02 7:30 ` Boris Brezillon
2015-07-02 7:30 ` Boris Brezillon
2015-07-20 7:16 ` Boris Brezillon
2015-07-20 7:16 ` Boris Brezillon
2015-07-20 7:16 ` Boris Brezillon
2015-07-20 7:43 ` Thierry Reding [this message]
2015-07-20 7:43 ` Thierry Reding
2015-07-20 7:43 ` Thierry Reding
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