From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Linus Walleij <linus.walleij@linaro.org>,
"thierry.reding@gmail.com" <thierry.reding@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ralf Baechle <ralf@linux-mips.org>,
paul.burton@mips.com, James Hogan <jhogan@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Mathieu Malaterre <malat@debian.org>,
ezequiel@collabora.co.uk, prasannatsmkumar@gmail.com,
linux-pwm@vger.kernel.org,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
<devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
LINUXWATCHDOG <linux-watchdog@vger.kernel.org>,
linux-mips@vger.kernel.org, linux-doc@vger.kernel.org,
linux-clk <linux-clk@vger.kernel.org>,
od@zcrc.me
Subject: Re: [PATCH v8 15/26] pwm: jz4740: Add support for the JZ4725B
Date: Mon, 17 Dec 2018 08:53:21 +0100 [thread overview]
Message-ID: <20181217075321.k45vhgnszeqs3tea@pengutronix.de> (raw)
In-Reply-To: <1544969932.1649.1@crapouillou.net>
On Sun, Dec 16, 2018 at 03:18:52PM +0100, Paul Cercueil wrote:
> Hi,
>
> Le ven. 14 déc. 2018 à 15:26, Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> a écrit :
> > Hello,
> >
> > On Fri, Dec 14, 2018 at 02:50:20PM +0100, Linus Walleij wrote:
> > > On Thu, Dec 13, 2018 at 9:42 PM Uwe Kleine-König
> > > <u.kleine-koenig@pengutronix.de> wrote:
> > > > [Adding Linus Walleij to Cc:]
> > > > On Thu, Dec 13, 2018 at 03:03:15PM +0100, Paul Cercueil wrote:
> > > > > Le jeu. 13 déc. 2018 à 10:24, Uwe Kleine-König
> > > > > <u.kleine-koenig@pengutronix.de> a écrit :
> > > > > > On Wed, Dec 12, 2018 at 11:09:10PM +0100, Paul Cercueil wrote:
> > > > > > > The PWM in the JZ4725B works the same as in the JZ4740,
> > > > > > > except that it only has 6 channels available instead of
> > > > > > > 8.
> > > > > >
> > > > > > this driver is probed only from device tree? If yes, it
> > > > > > might be sensible to specify the number of PWMs there and
> > > > > > get it from there.
> > > > > > There doesn't seem to be a generic binding for that, but there are
> > > > > > several drivers that could benefit from it. (This is a bigger project
> > > > > > though and shouldn't stop your patch. Still more as it already got
> > > > > > Thierry's ack.)
> > > > >
> > > > > I think there needs to be a proper guideline, as there doesn't seem to be
> > > > > a consensus about this. I learned from emails with Rob and Linus (Walleij)
> > > > > that I should not have in devicetree what I can deduce from the compatible
> > > > > string.
> > > >
> > > > I understood them a bit differently. It is ok to deduce things from the
> > > > compatible string. But if you define a generic property (say) "num-pwms"
> > > > that is used uniformly in most bindings this is ok, too. (And then the
> > > > two different devices could use the same compatible.)
> > > >
> > > > An upside of the generic "num-pwms" property is that the pwm core could
> > > > sanity check pwm phandles before passing them to the hardware drivers.
> > >
> > > I don't know if this helps, but in GPIO we have "ngpios" which is
> > > used to augment an existing block as to the number of lines actually
> > > used with it.
> > >
> > > The typical case is that an ASIC engineer synthesize a block for
> > > 32 GPIOs but only 12 of them are routed to external pads. So
> > > we augment the behaviour of that driver to only use 12 of the
> > > 32 lines.
> > >
> > > I guess using the remaining 20 lines "works" in a sense but they
> > > have no practical use and will just bias electrons in the silicon
> > > for no use.
> >
> > This looks very similar to the case under discussion.
> >
> > > So if the PWM case is something similar, then by all means add
> > > num-pwms.
> >
> > .. or "npwms" to use the same nomenclature as the gpio binding?
>
> If we're going to do something like this, should it be the drivers or
> the core (within pwmchip_add) that checks for this "npwms" property?
Of course this should be done in the core. The driver than can rely on
the validity of the index. But as I wrote before, this shouldn't stop
your patch from going in.
But if Thierry agrees that this npmws (or num-pwms) is a good idea, it
would be great to start early to convert drivers.
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |
next prev parent reply other threads:[~2018-12-17 7:53 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-12 22:08 [PATCH v8 00/26] Ingenic TCU patchset v8 Paul Cercueil
2018-12-12 22:08 ` [PATCH v8 01/26] dt-bindings: ingenic: Add DT bindings for TCU clocks Paul Cercueil
2018-12-17 23:18 ` Stephen Boyd
2018-12-12 22:08 ` [PATCH v8 02/26] doc: Add doc for the Ingenic TCU hardware Paul Cercueil
2018-12-12 22:08 ` [PATCH v8 03/26] dt-bindings: Add doc for the Ingenic TCU drivers Paul Cercueil
2018-12-17 21:05 ` Rob Herring
2018-12-17 22:03 ` Paul Cercueil
2018-12-18 16:36 ` Rob Herring
2018-12-22 11:09 ` Paul Cercueil
2018-12-12 22:08 ` [PATCH v8 04/26] clocksource: Add a new timer-ingenic driver Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 05/26] clocksource: Add driver for the Ingenic JZ47xx OST Paul Cercueil
2019-01-23 12:58 ` Mathieu Malaterre
2019-01-23 14:31 ` Guenter Roeck
2019-01-23 17:25 ` Paul Cercueil
2019-01-23 18:01 ` Guenter Roeck
2019-01-24 19:28 ` Stephen Boyd
2019-01-24 20:46 ` Paul Cercueil
2019-01-24 22:46 ` Stephen Boyd
2019-01-24 22:53 ` Paul Cercueil
2019-02-23 3:17 ` Paul Cercueil
2019-02-25 18:05 ` Stephen Boyd
2019-02-27 23:54 ` Paul Cercueil
2019-01-23 17:27 ` Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 06/26] MAINTAINERS: Add myself as maintainer for Ingenic TCU drivers Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 07/26] watchdog: jz4740: Use WDT clock provided by TCU driver Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 08/26] watchdog: jz4740: Use regmap " Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 09/26] watchdog: jz4740: Avoid starting watchdog in set_timeout Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 10/26] watchdog: jz4740: Drop dependency on MACH_JZ47xx, use COMPILE_TEST Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 11/26] pwm: jz4740: Use regmap and clocks from TCU driver Paul Cercueil
2018-12-13 9:30 ` Uwe Kleine-König
2018-12-13 14:34 ` Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 12/26] pwm: jz4740: Allow selection of PWM channels 0 and 1 Paul Cercueil
2018-12-13 9:18 ` Uwe Kleine-König
2018-12-13 13:58 ` Paul Cercueil
2018-12-13 20:32 ` Uwe Kleine-König
2018-12-16 13:36 ` Paul Cercueil
2018-12-17 7:43 ` Uwe Kleine-König
2018-12-12 22:09 ` [PATCH v8 13/26] pwm: jz4740: Drop dependency on MACH_INGENIC, use COMPILE_TEST Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 14/26] pwm: jz4740: Remove unused devicetree compatible strings Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 15/26] pwm: jz4740: Add support for the JZ4725B Paul Cercueil
2018-12-13 9:24 ` Uwe Kleine-König
2018-12-13 14:03 ` Paul Cercueil
2018-12-13 16:18 ` Thierry Reding
2018-12-13 20:42 ` Uwe Kleine-König
2018-12-14 13:50 ` Linus Walleij
2018-12-14 14:26 ` Uwe Kleine-König
2018-12-14 14:56 ` Linus Walleij
2018-12-16 14:18 ` Paul Cercueil
2018-12-17 7:53 ` Uwe Kleine-König [this message]
2018-12-20 17:39 ` Thierry Reding
2018-12-20 20:58 ` Uwe Kleine-König
2018-12-12 22:09 ` [PATCH v8 16/26] clk: jz4740: Add TCU clock Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 17/26] MIPS: Kconfig: Select TCU timer driver when MACH_INGENIC is set Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 18/26] MIPS: jz4740: Add DTS nodes for the TCU drivers Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 19/26] MIPS: qi_lb60: Move PWM devices to devicetree Paul Cercueil
2018-12-12 22:09 ` [PATCH v8 20/26] MIPS: qi_lb60: Reduce system timer and clocksource to 750 kHz Paul Cercueil
2018-12-12 22:12 ` [PATCH v8 21/26] MIPS: CI20: Reduce system timer and clocksource to 3 MHz Paul Cercueil
2018-12-12 22:12 ` [PATCH v8 22/26] MIPS: CI20: defconfig: enable OST driver Paul Cercueil
2018-12-12 22:13 ` [PATCH v8 23/26] MIPS: GCW0: Move clocksource to TCU channel 2 Paul Cercueil
2018-12-12 22:13 ` [PATCH v8 24/26] MIPS: GCW0: Reduce system timer and clocksource to 750 kHz Paul Cercueil
2018-12-12 22:14 ` [PATCH v8 25/26] MIPS: GCW0: defconfig: Enable OST, watchdog, PWM drivers Paul Cercueil
2018-12-12 22:15 ` [PATCH v8 26/26] MIPS: jz4740: Drop obsolete code Paul Cercueil
2019-01-24 21:26 ` [PATCH v8 00/26] Ingenic TCU patchset v8 Mathieu Malaterre
2019-01-24 21:41 ` Paul Cercueil
2019-01-25 8:21 ` Mathieu Malaterre
2019-01-25 17:04 ` Paul Cercueil
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