linux-kernel - Re: [PATCH 6/6] clk: samsung: Introduce Exynos850 clock driver

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Message-ID: <1428bfc4-520f-9af3-5255-b17308881243@gmail.com>
Date:   Thu, 16 Sep 2021 03:04:57 +0900
From:   Chanwoo Choi <cwchoi00@...il.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Paweł Chmiel <pawel.mikolaj.chmiel@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Tomasz Figa <tomasz.figa@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     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@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH 6/6] clk: samsung: Introduce Exynos850 clock driver

Hi Sam,

On 21. 9. 15. 오전 12:56, Sam Protsenko wrote:
> This is the initial implementation adding only basic clocks like UART,
> MMC, I2C and corresponding parent clocks. Design is influenced by
> Exynos7 and Exynos5433 clock drivers.
> 
> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
> ---
>   drivers/clk/samsung/Makefile        |   1 +
>   drivers/clk/samsung/clk-exynos850.c | 700 ++++++++++++++++++++++++++++
>   2 files changed, 701 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..1028caa2102e
> --- /dev/null
> +++ b/drivers/clk/samsung/clk-exynos850.c
> @@ -0,0 +1,700 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2021 Linaro Ltd.
> + * Author: Sam Protsenko <semen.protsenko@...aro.org>
> + *
> + * Common Clock Framework support for Exynos850 SoC.
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +
> +#include <dt-bindings/clock/exynos850.h>
> +
> +#include "clk.h"
> +
> +/* Gate register bits */
> +#define GATE_MANUAL		BIT(20)
> +#define GATE_ENABLE_HWACG	BIT(28)
> +
> +/* Gate register offsets range */
> +#define GATE_OFF_START		0x2000
> +#define GATE_OFF_END		0x2fff
> +
> +/**
> + * exynos850_init_clocks - Set clocks initial configuration
> + * @np:			CMU device tree node with "reg" property (CMU addr)
> + * @reg_offs:		Register offsets array for clocks to init
> + * @reg_offs_len:	Number of register offsets in reg_offs array
> + *
> + * Set manual control mode for all gate clocks.
> + */
> +static void __init exynos850_init_clocks(struct device_node *np,
> +		const unsigned long *reg_offs, size_t reg_offs_len)
> +{
> +	const __be32 *regaddr_p;
> +	u64 regaddr;
> +	u32 base;
> +	size_t i;
> +
> +	/* Get the base address ("reg" property in dts) */
> +	regaddr_p = of_get_address(np, 0, NULL, NULL);
> +	if (!regaddr_p)
> +		panic("%s: failed to get reg regaddr\n", __func__);
> +
> +	regaddr = of_translate_address(np, regaddr_p);
> +	if (regaddr == OF_BAD_ADDR || !regaddr)
> +		panic("%s: bad reg regaddr\n", __func__);
> +
> +	base = (u32)regaddr;
> +
> +	for (i = 0; i < reg_offs_len; ++i) {
> +		void __iomem *reg;
> +		u32 val;
> +
> +		/* Modify only gate clock registers */
> +		if (reg_offs[i] < GATE_OFF_START || reg_offs[i] > GATE_OFF_END)
> +			continue; > +
> +		reg = ioremap(base + reg_offs[i], 4);
> +		val = ioread32(reg);
> +		val |= GATE_MANUAL;
> +		val &= ~GATE_ENABLE_HWACG;
> +		iowrite32(val, reg);
> +		iounmap(reg);

I understand your intention for disabling HWACG.
But, it is not good to execute ioreamp/iounmap for each clock gate
register. I think that we need to consider the more pretty method
to initialize the clock register before clock registration.

[snip]

-- 
Best Regards,
Samsung Electronics
Chanwoo Choi