Message-ID: <1jv850hyvm.fsf@starbuckisacylon.baylibre.com>
Date: Tue, 02 Apr 2024 11:35:49 +0200
From: Jerome Brunet <jbrunet@...libre.com>
To: Dmitry Rokosov <ddrokosov@...utedevices.com>
Cc: neil.armstrong@...aro.org, jbrunet@...libre.com,
 mturquette@...libre.com, sboyd@...nel.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, khilman@...libre.com,
 martin.blumenstingl@...glemail.com, kernel@...utedevices.com,
 rockosov@...il.com, linux-amlogic@...ts.infradead.org,
 linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 6/6] clk: meson: a1: add Amlogic A1 CPU clock
 controller driver


On Fri 29 Mar 2024 at 23:58, Dmitry Rokosov <ddrokosov@...utedevices.com> wrote:

> The CPU clock controller plays a general role in the Amlogic A1 SoC
> family by generating CPU clocks. As an APB slave module, it offers the
> capability to inherit the CPU clock from two sources: the internal fixed
> clock known as 'cpu fixed clock' and the external input provided by the
> A1 PLL clock controller, referred to as 'syspll'.
>
> It is important for the driver to handle cpu_clk rate switching
> effectively by transitioning to the CPU fixed clock to avoid any
> potential execution freezes.
>
> Signed-off-by: Dmitry Rokosov <ddrokosov@...utedevices.com>
> ---
>  drivers/clk/meson/Kconfig  |  10 ++
>  drivers/clk/meson/Makefile |   1 +
>  drivers/clk/meson/a1-cpu.c | 324 +++++++++++++++++++++++++++++++++++++
>  drivers/clk/meson/a1-cpu.h |  16 ++
>  4 files changed, 351 insertions(+)
>  create mode 100644 drivers/clk/meson/a1-cpu.c
>  create mode 100644 drivers/clk/meson/a1-cpu.h
>
> diff --git a/drivers/clk/meson/Kconfig b/drivers/clk/meson/Kconfig
> index 80c4a18c83d2..148d4495eee3 100644
> --- a/drivers/clk/meson/Kconfig
> +++ b/drivers/clk/meson/Kconfig
> @@ -111,6 +111,16 @@ config COMMON_CLK_AXG_AUDIO
>  	  Support for the audio clock controller on AmLogic A113D devices,
>  	  aka axg, Say Y if you want audio subsystem to work.
>  
> +config COMMON_CLK_A1_CPU
> +	tristate "Amlogic A1 SoC CPU controller support"
> +	depends on ARM64
> +	select COMMON_CLK_MESON_REGMAP
> +	select COMMON_CLK_MESON_CLKC_UTILS
> +	help
> +	  Support for the CPU clock controller on Amlogic A113L based
> +	  device, A1 SoC Family. Say Y if you want A1 CPU clock controller
> +	  to work.
> +
>  config COMMON_CLK_A1_PLL
>  	tristate "Amlogic A1 SoC PLL controller support"
>  	depends on ARM64
> diff --git a/drivers/clk/meson/Makefile b/drivers/clk/meson/Makefile
> index 4968fc7ad555..2a06eb0303d6 100644
> --- a/drivers/clk/meson/Makefile
> +++ b/drivers/clk/meson/Makefile
> @@ -18,6 +18,7 @@ obj-$(CONFIG_COMMON_CLK_MESON_AUDIO_RSTC) += meson-audio-rstc.o
>  
>  obj-$(CONFIG_COMMON_CLK_AXG) += axg.o axg-aoclk.o
>  obj-$(CONFIG_COMMON_CLK_AXG_AUDIO) += axg-audio.o
> +obj-$(CONFIG_COMMON_CLK_A1_CPU) += a1-cpu.o
>  obj-$(CONFIG_COMMON_CLK_A1_PLL) += a1-pll.o
>  obj-$(CONFIG_COMMON_CLK_A1_PERIPHERALS) += a1-peripherals.o
>  obj-$(CONFIG_COMMON_CLK_A1_AUDIO) += a1-audio.o
> diff --git a/drivers/clk/meson/a1-cpu.c b/drivers/clk/meson/a1-cpu.c
> new file mode 100644
> index 000000000000..5f5d8ae112e5
> --- /dev/null
> +++ b/drivers/clk/meson/a1-cpu.c
> @@ -0,0 +1,324 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Amlogic A1 SoC family CPU Clock Controller driver.
> + *
> + * Copyright (c) 2024, SaluteDevices. All Rights Reserved.
> + * Author: Dmitry Rokosov <ddrokosov@...utedevices.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/platform_device.h>
> +#include "a1-cpu.h"
> +#include "clk-regmap.h"
> +#include "meson-clkc-utils.h"
> +
> +#include <dt-bindings/clock/amlogic,a1-cpu-clkc.h>
> +
> +static u32 cpu_fsource_sel_table[] = { 0, 1, 2 };
> +static const struct clk_parent_data cpu_fsource_sel_parents[] = {
> +	{ .fw_name = "xtal" },
> +	{ .fw_name = "fclk_div2" },
> +	{ .fw_name = "fclk_div3" },
> +};
> +
> +static struct clk_regmap cpu_fsource_sel0 = {
> +	.data = &(struct clk_regmap_mux_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.mask = 0x3,
> +		.shift = 0,
> +		.table = cpu_fsource_sel_table,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fsource_sel0",
> +		.ops = &clk_regmap_mux_ops,
> +		.parent_data = cpu_fsource_sel_parents,
> +		.num_parents = ARRAY_SIZE(cpu_fsource_sel_parents),
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_fsource_div0 = {
> +	.data = &(struct clk_regmap_div_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.shift = 4,
> +		.width = 6,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fsource_div0",
> +		.ops = &clk_regmap_divider_ops,
> +		.parent_hws = (const struct clk_hw *[]) {
> +			&cpu_fsource_sel0.hw
> +		},
> +		.num_parents = 1,
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_fsel0 = {
> +	.data = &(struct clk_regmap_mux_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.mask = 0x1,
> +		.shift = 2,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fsel0",
> +		.ops = &clk_regmap_mux_ops,
> +		.parent_hws = (const struct clk_hw *[]) {
> +			&cpu_fsource_sel0.hw,
> +			&cpu_fsource_div0.hw,
> +		},
> +		.num_parents = 2,
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_fsource_sel1 = {
> +	.data = &(struct clk_regmap_mux_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.mask = 0x3,
> +		.shift = 16,
> +		.table = cpu_fsource_sel_table,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fsource_sel1",
> +		.ops = &clk_regmap_mux_ops,
> +		.parent_data = cpu_fsource_sel_parents,
> +		.num_parents = ARRAY_SIZE(cpu_fsource_sel_parents),
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_fsource_div1 = {
> +	.data = &(struct clk_regmap_div_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.shift = 20,
> +		.width = 6,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fsource_div1",
> +		.ops = &clk_regmap_divider_ops,
> +		.parent_hws = (const struct clk_hw *[]) {
> +			&cpu_fsource_sel1.hw
> +		},
> +		.num_parents = 1,
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_fsel1 = {
> +	.data = &(struct clk_regmap_mux_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.mask = 0x1,
> +		.shift = 18,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fsel1",
> +		.ops = &clk_regmap_mux_ops,
> +		.parent_hws = (const struct clk_hw *[]) {
> +			&cpu_fsource_sel1.hw,
> +			&cpu_fsource_div1.hw,
> +		},
> +		.num_parents = 2,
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_fclk = {
> +	.data = &(struct clk_regmap_mux_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.mask = 0x1,
> +		.shift = 10,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_fclk",
> +		.ops = &clk_regmap_mux_ops,
> +		.parent_hws = (const struct clk_hw *[]) {
> +			&cpu_fsel0.hw,
> +			&cpu_fsel1.hw,
> +		},
> +		.num_parents = 2,
> +		.flags = CLK_SET_RATE_PARENT,
> +	},
> +};
> +
> +static struct clk_regmap cpu_clk = {
> +	.data = &(struct clk_regmap_mux_data) {
> +		.offset = CPUCTRL_CLK_CTRL0,
> +		.mask = 0x1,
> +		.shift = 11,
> +	},
> +	.hw.init = &(struct clk_init_data) {
> +		.name = "cpu_clk",
> +		.ops = &clk_regmap_mux_ops,
> +		.parent_data = (const struct clk_parent_data []) {
> +			{ .hw = &cpu_fclk.hw },
> +			{ .fw_name = "sys_pll", },
> +		},
> +		.num_parents = 2,
> +		.flags = CLK_SET_RATE_PARENT | CLK_IS_CRITICAL,
> +	},
> +};
> +
> +/* Array of all clocks registered by this provider */
> +static struct clk_hw *a1_cpu_hw_clks[] = {
> +	[CLKID_CPU_FSOURCE_SEL0]	= &cpu_fsource_sel0.hw,
> +	[CLKID_CPU_FSOURCE_DIV0]	= &cpu_fsource_div0.hw,
> +	[CLKID_CPU_FSEL0]		= &cpu_fsel0.hw,
> +	[CLKID_CPU_FSOURCE_SEL1]	= &cpu_fsource_sel1.hw,
> +	[CLKID_CPU_FSOURCE_DIV1]	= &cpu_fsource_div1.hw,
> +	[CLKID_CPU_FSEL1]		= &cpu_fsel1.hw,
> +	[CLKID_CPU_FCLK]		= &cpu_fclk.hw,
> +	[CLKID_CPU_CLK]			= &cpu_clk.hw,
> +};
> +
> +static struct clk_regmap *const a1_cpu_regmaps[] = {
> +	&cpu_fsource_sel0,
> +	&cpu_fsource_div0,
> +	&cpu_fsel0,
> +	&cpu_fsource_sel1,
> +	&cpu_fsource_div1,
> +	&cpu_fsel1,
> +	&cpu_fclk,
> +	&cpu_clk,
> +};
> +
> +static struct regmap_config a1_cpu_regmap_cfg = {
> +	.reg_bits   = 32,
> +	.val_bits   = 32,
> +	.reg_stride = 4,
> +	.max_register = CPUCTRL_CLK_CTRL1,
> +};
> +
> +static struct meson_clk_hw_data a1_cpu_clks = {
> +	.hws = a1_cpu_hw_clks,
> +	.num = ARRAY_SIZE(a1_cpu_hw_clks),
> +};
> +
> +struct a1_cpu_clk_nb_data {
> +	const struct clk_ops *mux_ops;

That's fishy ...

> +	struct clk_hw *cpu_clk;
> +	struct notifier_block nb;
> +	u8 parent;
> +};
> +
> +#define MESON_A1_CPU_CLK_GET_PARENT(nbd) \
> +	((nbd)->mux_ops->get_parent((nbd)->cpu_clk))
> +#define MESON_A1_CPU_CLK_SET_PARENT(nbd, index) \
> +	((nbd)->mux_ops->set_parent((nbd)->cpu_clk, index))

.. Directly going for the mux ops ??!?? No way !

We have a framework to handle the clocks, the whole point is to use it,
not bypass it ! 

> +
> +static int meson_a1_cpu_clk_notifier_cb(struct notifier_block *nb,
> +					unsigned long event, void *data)
> +{
> +	struct a1_cpu_clk_nb_data *nbd;
> +	int ret = 0;
> +
> +	nbd = container_of(nb, struct a1_cpu_clk_nb_data, nb);
> +
> +	switch (event) {
> +	case PRE_RATE_CHANGE:
> +		nbd->parent = MESON_A1_CPU_CLK_GET_PARENT(nbd);
> +		/* Fallback to the CPU fixed clock */
> +		ret = MESON_A1_CPU_CLK_SET_PARENT(nbd, 0);
> +		/* Wait for clock propagation */
> +		udelay(100);
> +		break;
> +
> +	case POST_RATE_CHANGE:
> +	case ABORT_RATE_CHANGE:
> +		/* Back to the original parent clock */
> +		ret = MESON_A1_CPU_CLK_SET_PARENT(nbd, nbd->parent);
> +		/* Wait for clock propagation */
> +		udelay(100);
> +		break;
> +
> +	default:
> +		pr_warn("Unknown event %lu for %s notifier block\n",
> +			event, clk_hw_get_name(nbd->cpu_clk));
> +		break;
> +	}
> +
> +	return notifier_from_errno(ret);
> +}
> +
> +static struct a1_cpu_clk_nb_data a1_cpu_clk_nb_data = {
> +	.mux_ops = &clk_regmap_mux_ops,
> +	.cpu_clk = &cpu_clk.hw,
> +	.nb.notifier_call = meson_a1_cpu_clk_notifier_cb,
> +};
> +
> +static int meson_a1_dvfs_setup(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct clk *notifier_clk;
> +	int ret;
> +
> +	/* Setup clock notifier for cpu_clk */
> +	notifier_clk = devm_clk_hw_get_clk(dev, &cpu_clk.hw, "dvfs");
> +	if (IS_ERR(notifier_clk))
> +		return dev_err_probe(dev, PTR_ERR(notifier_clk),
> +				     "can't get cpu_clk as notifier clock\n");
> +
> +	ret = devm_clk_notifier_register(dev, notifier_clk,
> +					 &a1_cpu_clk_nb_data.nb);
> +	if (ret)
> +		return dev_err_probe(dev, ret,
> +				     "can't register cpu_clk notifier\n");
> +
> +	return ret;
> +}
> +
> +static int meson_a1_cpu_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	void __iomem *base;
> +	struct regmap *map;
> +	int clkid, i, err;
> +
> +	base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(base))
> +		return dev_err_probe(dev, PTR_ERR(base),
> +				     "can't ioremap resource\n");
> +
> +	map = devm_regmap_init_mmio(dev, base, &a1_cpu_regmap_cfg);
> +	if (IS_ERR(map))
> +		return dev_err_probe(dev, PTR_ERR(map),
> +				     "can't init regmap mmio region\n");
> +
> +	/* Populate regmap for the regmap backed clocks */
> +	for (i = 0; i < ARRAY_SIZE(a1_cpu_regmaps); i++)
> +		a1_cpu_regmaps[i]->map = map;
> +
> +	for (clkid = 0; clkid < a1_cpu_clks.num; clkid++) {
> +		err = devm_clk_hw_register(dev, a1_cpu_clks.hws[clkid]);
> +		if (err)
> +			return dev_err_probe(dev, err,
> +					     "clock[%d] registration failed\n",
> +					     clkid);
> +	}
> +
> +	err = devm_of_clk_add_hw_provider(dev, meson_clk_hw_get, &a1_cpu_clks);
> +	if (err)
> +		return dev_err_probe(dev, err, "can't add clk hw provider\n");

I wonder if there is a window of opportunity to poke the syspll without
your notifier here. That being said, the situation would be similar on g12.

> +
> +	return meson_a1_dvfs_setup(pdev);



> +}
> +
> +static const struct of_device_id a1_cpu_clkc_match_table[] = {
> +	{ .compatible = "amlogic,a1-cpu-clkc", },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, a1_cpu_clkc_match_table);
> +
> +static struct platform_driver a1_cpu_clkc_driver = {
> +	.probe = meson_a1_cpu_probe,
> +	.driver = {
> +		.name = "a1-cpu-clkc",
> +		.of_match_table = a1_cpu_clkc_match_table,
> +	},
> +};
> +
> +module_platform_driver(a1_cpu_clkc_driver);
> +MODULE_AUTHOR("Dmitry Rokosov <ddrokosov@...utedevices.com>");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/clk/meson/a1-cpu.h b/drivers/clk/meson/a1-cpu.h
> new file mode 100644
> index 000000000000..e9af4117e26f
> --- /dev/null
> +++ b/drivers/clk/meson/a1-cpu.h

There is not point putting the definition here in a header
These are clearly not going to be shared with another driver.

Please drop this file

> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0+ */
> +/*
> + * Amlogic A1 CPU Clock Controller internals
> + *
> + * Copyright (c) 2024, SaluteDevices. All Rights Reserved.
> + * Author: Dmitry Rokosov <ddrokosov@...utedevices.com>
> + */
> +
> +#ifndef __A1_CPU_H
> +#define __A1_CPU_H
> +
> +/* cpu clock controller register offset */
> +#define CPUCTRL_CLK_CTRL0	0x80
> +#define CPUCTRL_CLK_CTRL1	0x84

You are claiming the registers from 0x00 to 0x84 (included), but only
using these 2 registers ? What is the rest ? Are you sure there is only
clocks in there ?

> +
> +#endif /* __A1_CPU_H */


-- 
Jerome

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