From: Lokesh Vutla <lokeshvutla@ti.com>
To: Richard Cochran <richardcochran@gmail.com>
Cc: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Thierry Reding" <thierry.reding@gmail.com>,
"Tony Lindgren" <tony@atomide.com>,
"Linux OMAP Mailing List" <linux-omap@vger.kernel.org>,
linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org,
"Sekhar Nori" <nsekhar@ti.com>, "Vignesh R" <vigneshr@ti.com>,
kernel@pengutronix.de
Subject: Re: [PATCH v3 4/5] pwm: omap-dmtimer: Do not disable pwm before changing period/duty_cycle
Date: Thu, 12 Mar 2020 22:44:08 +0530 [thread overview]
Message-ID: <b8750b79-8703-5d8f-eacf-b3a67cedd252@ti.com> (raw)
In-Reply-To: <20200312142126.GB2466@localhost>
Hi Richard,
On 12/03/20 7:51 PM, Richard Cochran wrote:
> On Thu, Mar 12, 2020 at 04:14:34PM +0530, Lokesh Vutla wrote:
>> But the problem here is that inactive breaks between two periods is not desired.
>> Because the pwm is used to generate a 1PPS signal and is continuously
>> synchronized with PTP clock.
>
> The 1-PPS case is the "easy" one. If the PWM is adjustable on the
> fly, then people will use it with higher frequency signals.
Yes, PWM can be adjusted on the fly. TRM does specify that corresponding
registers(TLDR, TMAR, TCRR) registers can be updated when timer is active.
>
>> I am up if this can be solved generically. But updating period is very specific
>> to hardware implementation. Not sure what generic solution can be brought out of
>> this. Please correct me if I am wrong.
>
> What happens today when the PWM frequency or duty cycle are changed
> while the signal is enabled?
Today, PWM is stopped and then period/duty_cycle are updated.
>
> Do different PWM devices/drivers behave the same way?
>
> Does this series change the behavior of the am335x and friends?
Yes, this series is applicable on all TI OMAP2+ devices with DMTIMER.
[0] http://www.ti.com/lit/ug/spruh73q/spruh73q.pdf Section 20.1.1.1 DMTIMER
overview Page 4436.
Thanks and regards,
Lokesh
next prev parent reply other threads:[~2020-03-12 17:15 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-12 4:22 [PATCH v3 0/5] pwm: omap-dmtimer: Allow for dynamic pwm period updates Lokesh Vutla
2020-03-12 4:22 ` [PATCH v3 1/5] pwm: omap-dmtimer: Drop unused header file Lokesh Vutla
2020-03-12 6:35 ` Uwe Kleine-König
2020-03-12 4:22 ` [PATCH v3 2/5] pwm: omap-dmtimer: Update description for pwm omap dm timer Lokesh Vutla
2020-03-12 6:35 ` Uwe Kleine-König
2020-03-12 4:22 ` [PATCH v3 3/5] pwm: omap-dmtimer: Fix pwm enabling sequence Lokesh Vutla
2020-03-12 4:22 ` [PATCH v3 4/5] pwm: omap-dmtimer: Do not disable pwm before changing period/duty_cycle Lokesh Vutla
2020-03-12 6:40 ` Uwe Kleine-König
2020-03-12 8:05 ` Lokesh Vutla
2020-03-12 8:47 ` Uwe Kleine-König
2020-03-12 10:44 ` Lokesh Vutla
2020-03-12 14:21 ` Richard Cochran
2020-03-12 17:14 ` Lokesh Vutla [this message]
2020-03-18 4:40 ` Lokesh Vutla
2020-03-30 14:14 ` Thierry Reding
2020-03-30 19:16 ` Uwe Kleine-König
2020-03-31 20:45 ` Thierry Reding
2020-04-01 8:22 ` Uwe Kleine-König
2020-04-01 10:22 ` Lokesh Vutla
2020-04-01 11:47 ` Uwe Kleine-König
2020-04-01 18:39 ` Thierry Reding
2020-04-01 20:36 ` Uwe Kleine-König
2020-04-01 18:28 ` Thierry Reding
2020-04-01 20:31 ` Uwe Kleine-König
2020-04-01 21:37 ` Thierry Reding
2020-04-02 14:02 ` Uwe Kleine-König
2020-04-03 8:51 ` Lokesh Vutla
2020-04-03 13:59 ` Uwe Kleine-König
2020-03-31 15:29 ` Lokesh Vutla
2020-03-31 20:10 ` Thierry Reding
2020-04-01 10:15 ` Lokesh Vutla
2020-03-12 4:22 ` [PATCH v3 5/5] pwm: omap-dmtimer: Implement .apply callback Lokesh Vutla
2020-03-13 15:31 ` Tony Lindgren
2020-03-23 11:30 ` [PATCH v3 0/5] pwm: omap-dmtimer: Allow for dynamic pwm period updates Lokesh Vutla
2020-03-30 14:04 ` Thierry Reding
Reply instructions:
You may reply publicly 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=b8750b79-8703-5d8f-eacf-b3a67cedd252@ti.com \
--to=lokeshvutla@ti.com \
--cc=kernel@pengutronix.de \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-omap@vger.kernel.org \
--cc=linux-pwm@vger.kernel.org \
--cc=nsekhar@ti.com \
--cc=richardcochran@gmail.com \
--cc=thierry.reding@gmail.com \
--cc=tony@atomide.com \
--cc=u.kleine-koenig@pengutronix.de \
--cc=vigneshr@ti.com \
/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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).