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Date: Tue, 10 Aug 2021 09:55:37 +0200 From: Sylwester Nawrocki <s.nawrocki@...sung.com> To: Sam Protsenko <semen.protsenko@...aro.org>, Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com> Cc: Chanwoo Choi <cw00.choi@...sung.com>, Linus Walleij <linus.walleij@...aro.org>, Tomasz Figa <tomasz.figa@...il.com>, Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>, Marc Zyngier <maz@...nel.org>, Rob Herring <robh+dt@...nel.org>, Stephen Boyd <sboyd@...nel.org>, Michael Turquette <mturquette@...libre.com>, Jiri Slaby <jirislaby@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>, Ryu Euiyoul <ryu.real@...sung.com>, Tom Gall <tom.gall@...aro.org>, Sumit Semwal <sumit.semwal@...aro.org>, John Stultz <john.stultz@...aro.org>, Amit Pundir <amit.pundir@...aro.org>, devicetree <devicetree@...r.kernel.org>, linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>, linux-clk <linux-clk@...r.kernel.org>, "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux Samsung SOC <linux-samsung-soc@...r.kernel.org>, "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org> Subject: Re: [PATCH v2 7/8] clk: samsung: Add Exynos850 clock driver stub 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. 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. -- Regards, Sylwester
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