Re: [PATCH 10/12] clk: samsung: Add Exynos850 clock driver stub

[Sam Protsenko <semen.protsenko@linaro.org>]

Hi Andy,

On Fri, 30 Jul 2021 at 18:12, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
>
> On Fri, Jul 30, 2021 at 5:51 PM Sam Protsenko
> <semen.protsenko@linaro.org> wrote:
> >
> > For now it's just a stub driver to make serial driver work. Later it
>
> make the serial
>
> > will be implemented properly.
> >
> > This driver doesn't really change clocks, only registers the UART clock
> > as a fixed-rate clock. Without this clock driver the UART driver won't
> > work, as it's trying to obtain "uart" clock and fails if it's not able
> > to.
>
>
> > From drivers/tty/serial/samsung_tty.c:
> >
> > 8<------------------------------------------------------------------->8
> >     ourport->clk = clk_get(&platdev->dev, "uart");
> >     if (IS_ERR(ourport->clk)) {
> >         pr_err("%s: Controller clock not found\n",
> >                 dev_name(&platdev->dev));
> >         ret = PTR_ERR(ourport->clk);
> >         goto err;
> >     }
> > 8<------------------------------------------------------------------->8
>
> This is not needed in the commit message.
>
> > In order to get functional serial console we have to implement that
>
> get a functional
>
> > minimal clock driver with "uart" clock. It's not necessary to actually
> > configure clocks, as those are already configured in bootloader, so
> > kernel can rely on that for now.
>
> > 80 column limit is broken here to make checkpatch happy, otherwise it
> > swears about incorrect __initconst usage.
>
> Again, no need to be in the commit message, use the comment field for
> this (after the cutter '---' line below).
>
>
> > Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
> > ---
> >  drivers/clk/samsung/Makefile        |  1 +
> >  drivers/clk/samsung/clk-exynos850.c | 63 +++++++++++++++++++++++++++++
> >  2 files changed, 64 insertions(+)
> >  create mode 100644 drivers/clk/samsung/clk-exynos850.c
> >
> > diff --git a/drivers/clk/samsung/Makefile b/drivers/clk/samsung/Makefile
> > index 028b2e27a37e..c46cf11e4d0b 100644
> > --- a/drivers/clk/samsung/Makefile
> > +++ b/drivers/clk/samsung/Makefile
> > @@ -17,6 +17,7 @@ obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK) += clk-exynos5433.o
> >  obj-$(CONFIG_EXYNOS_AUDSS_CLK_CON) += clk-exynos-audss.o
> >  obj-$(CONFIG_EXYNOS_CLKOUT)    += clk-exynos-clkout.o
> >  obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK)  += clk-exynos7.o
> > +obj-$(CONFIG_EXYNOS_ARM64_COMMON_CLK)  += clk-exynos850.o
> >  obj-$(CONFIG_S3C2410_COMMON_CLK)+= clk-s3c2410.o
> >  obj-$(CONFIG_S3C2410_COMMON_DCLK)+= clk-s3c2410-dclk.o
> >  obj-$(CONFIG_S3C2412_COMMON_CLK)+= clk-s3c2412.o
> > diff --git a/drivers/clk/samsung/clk-exynos850.c b/drivers/clk/samsung/clk-exynos850.c
> > new file mode 100644
> > index 000000000000..3192ec9bb90b
> > --- /dev/null
> > +++ b/drivers/clk/samsung/clk-exynos850.c
> > @@ -0,0 +1,63 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright (C) 2019 Samsung Electronics Co., Ltd.
> > + * Copyright (C) 2021 Linaro Ltd.
> > + *
> > + * Common Clock Framework support for Exynos850 SoC.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/clkdev.h>
> > +#include <linux/clk-provider.h>
> > +#include <linux/of.h>
> > +#include <linux/of_address.h>
>
> + blank line?
>
> > +#include <dt-bindings/clock/exynos850.h>
> > +
> > +#include "clk.h"
> > +
> > +/* 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", .data = (void *)0 },
>
> 0 is the default for static variables.
>
> > +       {},
>
> No comma needed for the terminator lines.
>
> > +};
> > +
> > +void __init exynos850_clk_init(struct device_node *np)
> > +{
> > +       void __iomem *reg_base;
> > +       struct samsung_clk_provider *ctx;
>
> > +       if (!np)
> > +               panic("%s: unable to determine soc\n", __func__);
>
> Check for the sake of additional code?
>
> > +       reg_base = of_iomap(np, 0);
>
> This will fail when np == NULL.
>

Thanks for the review! All your comments will be addressed in v2.

> > +       if (!reg_base)
> > +               panic("%s: failed to map registers\n", __func__);
> > +
> > +       ctx = samsung_clk_init(np, reg_base, CLK_NR_CLKS);
> > +       if (!ctx)
> > +               panic("%s: unable to allocate ctx\n", __func__);
> > +
> > +       samsung_clk_of_register_fixed_ext(ctx,
> > +                       exynos850_fixed_rate_ext_clks,
> > +                       ARRAY_SIZE(exynos850_fixed_rate_ext_clks),
> > +                       ext_clk_match);
> > +
> > +       samsung_clk_register_fixed_rate(ctx, exynos850_peri_clks,
> > +                       ARRAY_SIZE(exynos850_peri_clks));
> > +
> > +       samsung_clk_of_add_provider(np, ctx);
> > +}
> > +
> > +CLK_OF_DECLARE(exynos850_clk, "samsung,exynos850-clock", exynos850_clk_init);
>
>
> --
> With Best Regards,
> Andy Shevchenko