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From: Sam Protsenko <semen.protsenko@linaro.org>
To: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: "Krzysztof Kozlowski" <krzysztof.kozlowski@canonical.com>,
	"Chanwoo Choi" <cw00.choi@samsung.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Tomasz Figa" <tomasz.figa@gmail.com>,
	"Paweł Chmiel" <pawel.mikolaj.chmiel@gmail.com>,
	"Marc Zyngier" <maz@kernel.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Stephen Boyd" <sboyd@kernel.org>,
	"Michael Turquette" <mturquette@baylibre.com>,
	"Jiri Slaby" <jirislaby@kernel.org>,
	"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
	"Charles Keepax" <ckeepax@opensource.wolfsonmicro.com>,
	"Ryu Euiyoul" <ryu.real@samsung.com>,
	"Tom Gall" <tom.gall@linaro.org>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"John Stultz" <john.stultz@linaro.org>,
	"Amit Pundir" <amit.pundir@linaro.org>,
	devicetree <devicetree@vger.kernel.org>,
	"linux-arm Mailing List" <linux-arm-kernel@lists.infradead.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Linux Samsung SOC" <linux-samsung-soc@vger.kernel.org>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>
Subject: Re: [PATCH v2 7/8] clk: samsung: Add Exynos850 clock driver stub
Date: Wed, 11 Aug 2021 14:20:02 +0300	[thread overview]
Message-ID: <CAPLW+4mPrPSeukiJY6DmpEz0V=bjEYbjzLTnJ28T01yqoQY=mg@mail.gmail.com> (raw)
In-Reply-To: <bb69e79d-55a8-2090-e51c-fdfea755cf99@samsung.com>

On Tue, 10 Aug 2021 at 10:55, Sylwester Nawrocki <s.nawrocki@samsung.com> wrote:
>
> On 09.08.2021 21:48, Sam Protsenko wrote:
> >>> +/* Will be extracted to bindings header once proper clk driver is implemented */
> >>> +#define OSCCLK               1
> >>> +#define DOUT_UART    2
> >>> +#define CLK_NR_CLKS  3
> >>> +
> >>> +/* Fixed rate clocks generated outside the SoC */
> >>> +static struct samsung_fixed_rate_clock exynos850_fixed_rate_ext_clks[] __initdata = {
> >>> +     FRATE(OSCCLK, "fin_pll", NULL, 0, 26000000),
> >>> +};
> >>> +
> >>> +/*
> >>> + * Model the UART clock as a fixed-rate clock for now, to make serial driver
> >>> + * work. This clock is already configured in the bootloader.
> >>> + */
> >>> +static const struct samsung_fixed_rate_clock exynos850_peri_clks[] __initconst = {
> >>> +     FRATE(DOUT_UART, "DOUT_UART", NULL, 0, 200000000),
> >>> +};
> >>> +
> >>> +static const struct of_device_id ext_clk_match[] __initconst = {
> >>> +     { .compatible = "samsung,exynos850-oscclk" },
> >>
> >> One more thing - I am not sure anymore if this is correct. AFAIR, we
> >> wanted to drop compatibles for external clocks.
> >>
> > I'll remove oscclk from the clock driver and device tree. It's not
> > needed right now anyway, as that driver is just a stub.
> >
> > But I'd still like to know the proper way to define external clocks. I
> > can see that in exynos7.dtsi and exynos5433.dtsi there is just regular
> > fixed clock defined for "oscclk" (or "fin_pll"), and then that clock
> > is referenced in corresponding clock driver by its
> > 'clock-output-names' property. I guess that approach is the
> > recommended one?
>
> Yes, we should use generic "fixed-clock" in DT to model the external
> root clock. Registering the external clock from within the CMU driver
> is a legacy method that predates generic "fixed-clock" and should be
> avoided.
>

Thanks for confirming this. I'll go with generic fixed clock in my
clock patch series then.

> That said I think this temporary stub driver is not needed at all,
> you could well define a fixed clock in DT and reference it in the UART
> node, as Krzysztof suggested.
>

Ok, I'll remove the stub clock driver in v3. Using fixed clock in
device tree for serial seems to work fine.

> --
> Regards,
> Sylwester

  reply	other threads:[~2021-08-11 11:20 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-06 15:21 [PATCH v2 0/8] Add minimal support for Exynos850 SoC Sam Protsenko
2021-08-06 15:21 ` [PATCH v2 1/8] dt-bindings: pinctrl: samsung: Add Exynos850 doc Sam Protsenko
2021-08-06 15:21 ` [PATCH v2 2/8] pinctrl: samsung: Add Exynos850 SoC specific data Sam Protsenko
2021-08-09 10:43   ` Krzysztof Kozlowski
2021-08-09 18:18     ` Sam Protsenko
2021-08-06 15:21 ` [PATCH v2 3/8] dt-bindings: serial: samsung: Add Exynos850 doc Sam Protsenko
2021-08-06 15:21 ` [PATCH v2 4/8] tty: serial: samsung: Init USI to keep clocks running Sam Protsenko
2021-08-09 10:45   ` Krzysztof Kozlowski
2021-08-06 15:21 ` [PATCH v2 5/8] tty: serial: samsung: Fix driver data macros style Sam Protsenko
2021-08-06 15:21 ` [PATCH v2 6/8] tty: serial: samsung: Add Exynos850 SoC data Sam Protsenko
2021-08-09 10:46   ` Krzysztof Kozlowski
2021-08-06 15:21 ` [PATCH v2 7/8] clk: samsung: Add Exynos850 clock driver stub Sam Protsenko
2021-08-09 10:55   ` Krzysztof Kozlowski
2021-08-09 18:51     ` Sam Protsenko
2021-08-09 11:22   ` Krzysztof Kozlowski
2021-08-09 19:48     ` Sam Protsenko
2021-08-10  7:55       ` Sylwester Nawrocki
2021-08-11 11:20         ` Sam Protsenko [this message]
2021-08-06 15:21 ` [PATCH v2 8/8] arm64: dts: exynos: Add Exynos850 SoC support Sam Protsenko

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