From: Paul Cercueil <paul@crapouillou.net>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: linux-pwm@vger.kernel.org,
Thierry Reding <thierry.reding@gmail.com>,
kernel@pengutronix.de
Subject: Re: [PATCH] pwm: jz4740: document known limitations
Date: Fri, 09 Aug 2019 02:08:20 +0200 [thread overview]
Message-ID: <1565309300.15950.2@crapouillou.net> (raw)
In-Reply-To: <20190807134915.njgbpbfsy44aqba6@pengutronix.de>
Le mer. 7 août 2019 à 15:49, Uwe =?iso-8859-1?q?Kleine-K=F6nig?=
<u.kleine-koenig@pengutronix.de> a écrit :
> On Wed, Aug 07, 2019 at 03:42:31PM +0200, Paul Cercueil wrote:
>>
>>
>> Le mar. 30 juil. 2019 à 14:32, Uwe =?iso-8859-1?q?Kleine-K=F6nig?=
>> <u.kleine-koenig@pengutronix.de> a écrit :
>> > The jz4740 PMW implementation doesn't fulfill the (up to now
>> > insufficiently documented) requirements of the PWM API. At least
>> > document them in the driver.
>> >
>> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
>> > ---
>> > I intended to also add a Link to the reference manual, Paul
>> suggested to
>> > use https://zcrc.me/~paul/jz_docs/ in December last year, but this
>> > stopped to work.
>> >
>> > The second item is something I noticed when reading through the
>> manual,
>> > but it's not confirmed in practise. A test that this is indeed
>> the case
>> > could be done by configuring a long period (say 5s) and a (in
>> > comparison) small duty-cycle (say 1s). If the pwm output isn't
>> active
>> > when the call returns I'd consider this proven.
>> >
>> > @Paul: would you mind doing this test?
>>
>> You're correct. I configured it for 4s period and 2s duty. After
>> enabling
>> the
>> PWM, it stays LOW for two seconds then switches HIGH for two
>> seconds.
>>
>> That can be corrected, though, by inverting the configured polarity
>> when the
>> PWM is running and set "period - duty" as the duty value. I can
>> make a patch
>> for that.
>
> OK. Do you care for documenting the first limitation then, too?
>
> Or should we apply my patch as is and you remote the second item when
> you fix it?
Actually ignore my previous answer, I'll send a patchset very soon and
I have the
patch ready, so I'll document the first limit in the patchset.
-Paul
> Best regards
> Uwe
>
> --
> Pengutronix e.K. | Uwe Kleine-König
> |
> Industrial Linux Solutions |
> http://www.pengutronix.de/ |
next prev parent reply other threads:[~2019-08-09 0:08 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-07 15:44 [PATCH v2 0/6] PWM JZ4740 fixes and cleanups Paul Cercueil
2019-06-07 15:44 ` [PATCH v2 1/6] dt-bindings: Remove unused compatible strings Paul Cercueil
2019-07-09 2:04 ` Rob Herring
2019-07-09 3:18 ` Paul Cercueil
2019-07-09 15:46 ` Rob Herring
2019-08-08 8:28 ` Uwe Kleine-König
2019-08-12 23:39 ` Rob Herring
2019-06-07 15:44 ` [PATCH v2 2/6] pwm: jz4740: Remove unused devicetree " Paul Cercueil
2019-08-08 8:24 ` Uwe Kleine-König
2019-06-07 15:44 ` [PATCH v2 3/6] pwm: jz4740: Apply configuration atomically Paul Cercueil
2019-07-22 19:34 ` Uwe Kleine-König
2019-07-23 20:46 ` Paul Cercueil
2019-07-24 6:47 ` Uwe Kleine-König
2019-07-29 21:19 ` Paul Cercueil
2019-07-30 12:32 ` [PATCH] pwm: jz4740: document known limitations Uwe Kleine-König
2019-08-07 13:42 ` Paul Cercueil
2019-08-07 13:49 ` Uwe Kleine-König
2019-08-07 18:40 ` Paul Cercueil
2019-08-09 0:08 ` Paul Cercueil [this message]
2019-08-07 13:53 ` Paul Cercueil
2019-06-07 15:44 ` [PATCH v2 4/6] pwm: jz4740: Drop dependency on MACH_INGENIC Paul Cercueil
2019-06-07 15:44 ` [PATCH v2 5/6] pwm: jz4740: Force TCU2 channels to return to their init level Paul Cercueil
2019-06-07 15:44 ` [PATCH v2 6/6] pwm: jz4740: Use __init_or_module and __exit for .probe and .remove Paul Cercueil
2019-06-08 10:31 ` Paul Cercueil
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