Re: [PATCH v1 1/3] dt-bindings: pwm: Add binding for Allwinner D1/T113-S3/R329 PWM controller

From: Conor Dooley <conor@kernel.org>
To: "Александр Шубин" <privatesub2@gmail.com>
Cc: linux-kernel@vger.kernel.org,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Chen-Yu Tsai" <wens@csie.org>,
	"Jernej Skrabec" <jernej.skrabec@gmail.com>,
	"Samuel Holland" <samuel@sholland.org>,
	"Paul Walmsley" <paul.walmsley@sifive.com>,
	"Palmer Dabbelt" <palmer@dabbelt.com>,
	"Albert Ou" <aou@eecs.berkeley.edu>,
	"Philipp Zabel" <p.zabel@pengutronix.de>,
	"Cristian Ciocaltea" <cristian.ciocaltea@collabora.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	linux-pwm@vger.kernel.org, devicetree@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-sunxi@lists.linux.dev, linux-riscv@lists.infradead.org
Subject: Re: [PATCH v1 1/3] dt-bindings: pwm: Add binding for Allwinner D1/T113-S3/R329 PWM controller
Date: Fri, 16 Jun 2023 19:57:05 +0100	[thread overview]
Message-ID: <20230616-stopped-bunny-619cf684c9cb@spud> (raw)
In-Reply-To: <CAF4idNksCzkh0WMhvb7ecqYfJRLw33GrpT1+eL5S9ydS8Uu-BA@mail.gmail.com>

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On Fri, Jun 16, 2023 at 11:02:12AM +0300, Александр Шубин wrote:
> чт, 15 июн. 2023 г. в 19:37, Conor Dooley <conor@kernel.org>:
> > On Thu, Jun 15, 2023 at 05:43:56PM +0300, Aleksandr Shubin wrote:
> > > Allwinner's D1, T113-S3 and R329 SoCs have a new pwm
> > > controller witch is different from the previous pwm-sun4i.
> > >
> > > D1 and T113s SoCs have one PWM controller with 8 channels.
> > > R329 SoC has two PWM controllers in both power domains, one of
> > > them has 9 channels (CPUX one) and the other has 6 (CPUS one).
> >
> > It would be good to note that the D1 and T113 are identical in terms of
> > peripherals, they differ only in the architecture of the CPU core, and
> > even share the majority of their DT. Because of that, using the same
> > compatible makes sense.
> > The R329 is a different SoC though, and should have a different
> > compatible string added, especially as there is a difference in the
> > number of channels. It would be fine to use the current compatible for
> > the D1 as a fallback.
> > The allwinner,pwm-channels property should probably only be allowed on
> > the R329 and only allow the values of 6 & 9.
> 
> 
> Maybe would it be better to allow only 8 channels for D1 and only 6 and 9
> channels for R329?

If you're on a D1, you don't need a dt property to tell you the number
of channels, you already know it to be 8. Couple ways driver could
implement that, for example: if the dt-binding requires the property on
the R329, you could set 8 as the default and overwrite it if the
property exists - which would only be permitted on the R329.
Up to you.

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