Message-ID: <20150728105348.7cea3eb1@bbrezillon>
Date:	Tue, 28 Jul 2015 10:53:48 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Nicolas Ferre <nicolas.ferre@...el.com>
Cc:	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Josh Wu <josh.wu@...el.com>, <mturquette@...libre.com>,
	<pebolle@...cali.nl>
Subject: Re: [PATCH v3] clk: at91: add generated clock driver

On Mon, 27 Jul 2015 18:39:15 +0200
Nicolas Ferre <nicolas.ferre@...el.com> wrote:

> Add a new type of clocks that can be provided to a peripheral.
> In addition to the peripheral clock, this new clock that can use several
> input clocks as parents can generate divided rates.
> This would allow a peripheral to have finer grained clocks for generating
> a baud rate, clocking an asynchronous part or having more
> options in frequency.
> 
> Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>

Acked-by: Boris Brezillon <boris.brezillon@...e-electrons.com>

> ---
> 
> Changes in v3:
> - rebase on top of next-20150727
> - make use of of_clk_parent_fill helper function
> - change determine_rate() according to new prototype
> 
> Changes in v2:
> - adapt to new xxx_determine_rate() callback prototype
> - fix checkpatch errors and use __func__
> - fix handling of clocks without clk-output-range property specified.
>   Test if range.max is present before using it
> - test clock id only at probe time instead of at each API call
> - remove useless tests in clk_generated_set_rate()
> - change the meaningless config HAVE_AT91_GENERATED to HAVE_AT91_GENERATED_CLK
> - wrap some lines over 80 characters
> 
>  .../devicetree/bindings/clock/at91-clock.txt       |  35 +++
>  arch/arm/mach-at91/Kconfig                         |   3 +
>  drivers/clk/at91/Makefile                          |   1 +
>  drivers/clk/at91/clk-generated.c                   | 306 +++++++++++++++++++++
>  drivers/clk/at91/pmc.c                             |   6 +
>  drivers/clk/at91/pmc.h                             |   3 +
>  include/linux/clk/at91_pmc.h                       |   7 +
>  7 files changed, 361 insertions(+)
>  create mode 100644 drivers/clk/at91/clk-generated.c
> 
> diff --git a/Documentation/devicetree/bindings/clock/at91-clock.txt b/Documentation/devicetree/bindings/clock/at91-clock.txt
> index 5ba6450693b9..5e737d2cd05d 100644
> --- a/Documentation/devicetree/bindings/clock/at91-clock.txt
> +++ b/Documentation/devicetree/bindings/clock/at91-clock.txt
> @@ -77,6 +77,9 @@ Required properties:
>  	"atmel,sama5d4-clk-h32mx":
>  		at91 h32mx clock
>  
> +	"atmel,sama5d2-clk-generated":
> +		at91 generated clock
> +
>  Required properties for SCKC node:
>  - reg : defines the IO memory reserved for the SCKC.
>  - #size-cells : shall be 0 (reg is used to encode clk id).
> @@ -461,3 +464,35 @@ For example:
>  		compatible = "atmel,sama5d4-clk-h32mx";
>  		clocks = <&mck>;
>  	};
> +
> +Required properties for generated clocks:
> +- #size-cells : shall be 0 (reg is used to encode clk id).
> +- #address-cells : shall be 1 (reg is used to encode clk id).
> +- clocks : shall be the generated clock source phandles.
> +	e.g. clocks = <&clk32k>, <&main>, <&plladiv>, <&utmi>, <&mck>;
> +- name: device tree node describing a specific generated clock.
> +	* #clock-cells : from common clock binding; shall be set to 0.
> +	* reg: peripheral id. See Atmel's datasheets to get a full
> +	  list of peripheral ids.
> +	* atmel,clk-output-range : minimum and maximum clock frequency
> +	  (two u32 fields).
> +
> +For example:
> +	gck {
> +		compatible = "atmel,sama5d2-clk-generated";
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +		clocks = <&clk32k>, <&main>, <&plladiv>, <&utmi>, <&mck>;
> +
> +		tcb0_gclk: tcb0_gclk {
> +			#clock-cells = <0>;
> +			reg = <35>;
> +			atmel,clk-output-range = <0 83000000>;
> +		};
> +
> +		pwm_gclk: pwm_gclk {
> +			#clock-cells = <0>;
> +			reg = <38>;
> +			atmel,clk-output-range = <0 83000000>;
> +		};
> +	};
> diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
> index fd95f34945f4..e8273e79f6ba 100644
> --- a/arch/arm/mach-at91/Kconfig
> +++ b/arch/arm/mach-at91/Kconfig
> @@ -90,6 +90,9 @@ config HAVE_AT91_SMD
>  config HAVE_AT91_H32MX
>  	bool
>  
> +config HAVE_AT91_GENERATED_CLK
> +	bool
> +
>  config SOC_SAM_V4_V5
>  	bool
>  
> diff --git a/drivers/clk/at91/Makefile b/drivers/clk/at91/Makefile
> index 89a48a7bd5df..13e67bd35cff 100644
> --- a/drivers/clk/at91/Makefile
> +++ b/drivers/clk/at91/Makefile
> @@ -10,3 +10,4 @@ obj-$(CONFIG_HAVE_AT91_UTMI)		+= clk-utmi.o
>  obj-$(CONFIG_HAVE_AT91_USB_CLK)		+= clk-usb.o
>  obj-$(CONFIG_HAVE_AT91_SMD)		+= clk-smd.o
>  obj-$(CONFIG_HAVE_AT91_H32MX)		+= clk-h32mx.o
> +obj-$(CONFIG_HAVE_AT91_GENERATED_CLK)	+= clk-generated.o
> diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c
> new file mode 100644
> index 000000000000..473e8781bc2d
> --- /dev/null
> +++ b/drivers/clk/at91/clk-generated.c
> @@ -0,0 +1,306 @@
> +/*
> + *  Copyright (C) 2015 Atmel Corporation,
> + *                     Nicolas Ferre <nicolas.ferre@...el.com>
> + *
> + * Based on clk-programmable & clk-peripheral drivers by Boris BREZILLON.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + */
> +
> +#include <linux/clk-provider.h>
> +#include <linux/clkdev.h>
> +#include <linux/clk/at91_pmc.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/io.h>
> +
> +#include "pmc.h"
> +
> +#define PERIPHERAL_MAX		64
> +#define PERIPHERAL_ID_MIN	2
> +
> +#define GENERATED_SOURCE_MAX	6
> +#define GENERATED_MAX_DIV	255
> +
> +struct clk_generated {
> +	struct clk_hw hw;
> +	struct at91_pmc *pmc;
> +	struct clk_range range;
> +	u32 id;
> +	u32 gckdiv;
> +	u8 parent_id;
> +};
> +
> +#define to_clk_generated(hw) \
> +	container_of(hw, struct clk_generated, hw)
> +
> +static int clk_generated_enable(struct clk_hw *hw)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +	struct at91_pmc *pmc = gck->pmc;
> +	u32 tmp;
> +
> +	pr_debug("GCLK: %s, gckdiv = %d, parent id = %d\n",
> +		 __func__, gck->gckdiv, gck->parent_id);
> +
> +	pmc_lock(pmc);
> +	pmc_write(pmc, AT91_PMC_PCR, (gck->id & AT91_PMC_PCR_PID_MASK));
> +	tmp = pmc_read(pmc, AT91_PMC_PCR) &
> +			~(AT91_PMC_PCR_GCKDIV_MASK | AT91_PMC_PCR_GCKCSS_MASK);
> +	pmc_write(pmc, AT91_PMC_PCR, tmp | AT91_PMC_PCR_GCKCSS(gck->parent_id)
> +					 | AT91_PMC_PCR_CMD
> +					 | AT91_PMC_PCR_GCKDIV(gck->gckdiv)
> +					 | AT91_PMC_PCR_GCKEN);
> +	pmc_unlock(pmc);
> +	return 0;
> +}
> +
> +static void clk_generated_disable(struct clk_hw *hw)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +	struct at91_pmc *pmc = gck->pmc;
> +	u32 tmp;
> +
> +	pmc_lock(pmc);
> +	pmc_write(pmc, AT91_PMC_PCR, (gck->id & AT91_PMC_PCR_PID_MASK));
> +	tmp = pmc_read(pmc, AT91_PMC_PCR) & ~AT91_PMC_PCR_GCKEN;
> +	pmc_write(pmc, AT91_PMC_PCR, tmp | AT91_PMC_PCR_CMD);
> +	pmc_unlock(pmc);
> +}
> +
> +static int clk_generated_is_enabled(struct clk_hw *hw)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +	struct at91_pmc *pmc = gck->pmc;
> +	int ret;
> +
> +	pmc_lock(pmc);
> +	pmc_write(pmc, AT91_PMC_PCR, (gck->id & AT91_PMC_PCR_PID_MASK));
> +	ret = !!(pmc_read(pmc, AT91_PMC_PCR) & AT91_PMC_PCR_GCKEN);
> +	pmc_unlock(pmc);
> +
> +	return ret;
> +}
> +
> +static unsigned long
> +clk_generated_recalc_rate(struct clk_hw *hw,
> +			  unsigned long parent_rate)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +
> +	return DIV_ROUND_CLOSEST(parent_rate, gck->gckdiv + 1);
> +}
> +
> +static int clk_generated_determine_rate(struct clk_hw *hw,
> +					struct clk_rate_request *req)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +	struct clk *parent = NULL;
> +	long best_rate = -EINVAL;
> +	unsigned long tmp_rate, min_rate;
> +	int best_diff = -1;
> +	int tmp_diff;
> +	int i;
> +
> +	for (i = 0; i < __clk_get_num_parents(hw->clk); i++) {
> +		u32 div;
> +		unsigned long parent_rate;
> +
> +		parent = clk_get_parent_by_index(hw->clk, i);
> +		if (!parent)
> +			continue;
> +
> +		parent_rate = __clk_get_rate(parent);
> +		min_rate = DIV_ROUND_CLOSEST(parent_rate, GENERATED_MAX_DIV + 1);
> +		if (!parent_rate ||
> +		    (gck->range.max && min_rate > gck->range.max))
> +			continue;
> +
> +		for (div = 1; div < GENERATED_MAX_DIV + 2; div++) {
> +			tmp_rate = DIV_ROUND_CLOSEST(parent_rate, div);
> +			tmp_diff = abs(req->rate - tmp_rate);
> +
> +			if (best_diff < 0 || best_diff > tmp_diff) {
> +				best_rate = tmp_rate;
> +				best_diff = tmp_diff;
> +				req->best_parent_rate = parent_rate;
> +				req->best_parent_hw = __clk_get_hw(parent);
> +			}
> +
> +			if (!best_diff || tmp_rate < req->rate)
> +				break;
> +		}
> +
> +		if (!best_diff)
> +			break;
> +	}
> +
> +	pr_debug("GCLK: %s, best_rate = %ld, parent clk: %s @ %ld\n",
> +		 __func__, best_rate,
> +		 __clk_get_name((req->best_parent_hw)->clk),
> +		 req->best_parent_rate);
> +
> +	if (best_rate < 0)
> +		return best_rate;
> +
> +	req->rate = best_rate;
> +	return 0;
> +}
> +
> +/* No modification of hardware as we have the flag CLK_SET_PARENT_GATE set */
> +static int clk_generated_set_parent(struct clk_hw *hw, u8 index)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +
> +	if (index >= __clk_get_num_parents(hw->clk))
> +		return -EINVAL;
> +
> +	gck->parent_id = index;
> +	return 0;
> +}
> +
> +static u8 clk_generated_get_parent(struct clk_hw *hw)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +
> +	return gck->parent_id;
> +}
> +
> +/* No modification of hardware as we have the flag CLK_SET_RATE_GATE set */
> +static int clk_generated_set_rate(struct clk_hw *hw,
> +				  unsigned long rate,
> +				  unsigned long parent_rate)
> +{
> +	struct clk_generated *gck = to_clk_generated(hw);
> +	u32 div;
> +
> +	if (!rate)
> +		return -EINVAL;
> +
> +	if (gck->range.max && rate > gck->range.max)
> +		return -EINVAL;
> +
> +	div = DIV_ROUND_CLOSEST(parent_rate, rate);
> +	if (div > GENERATED_MAX_DIV + 1 || !div)
> +		return -EINVAL;
> +
> +	gck->gckdiv = div - 1;
> +	return 0;
> +}
> +
> +static const struct clk_ops generated_ops = {
> +	.enable = clk_generated_enable,
> +	.disable = clk_generated_disable,
> +	.is_enabled = clk_generated_is_enabled,
> +	.recalc_rate = clk_generated_recalc_rate,
> +	.determine_rate = clk_generated_determine_rate,
> +	.get_parent = clk_generated_get_parent,
> +	.set_parent = clk_generated_set_parent,
> +	.set_rate = clk_generated_set_rate,
> +};
> +
> +/**
> + * clk_generated_startup - Initialize a given clock to its default parent and
> + * divisor parameter.
> + *
> + * @gck:	Generated clock to set the startup parameters for.
> + *
> + * Take parameters from the hardware and update local clock configuration
> + * accordingly.
> + */
> +static void clk_generated_startup(struct clk_generated *gck)
> +{
> +	struct at91_pmc *pmc = gck->pmc;
> +	u32 tmp;
> +
> +	pmc_lock(pmc);
> +	pmc_write(pmc, AT91_PMC_PCR, (gck->id & AT91_PMC_PCR_PID_MASK));
> +	tmp = pmc_read(pmc, AT91_PMC_PCR);
> +	pmc_unlock(pmc);
> +
> +	gck->parent_id = (tmp & AT91_PMC_PCR_GCKCSS_MASK)
> +					>> AT91_PMC_PCR_GCKCSS_OFFSET;
> +	gck->gckdiv = (tmp & AT91_PMC_PCR_GCKDIV_MASK)
> +					>> AT91_PMC_PCR_GCKDIV_OFFSET;
> +}
> +
> +static struct clk * __init
> +at91_clk_register_generated(struct at91_pmc *pmc, const char *name,
> +			    const char **parent_names, u8 num_parents,
> +			    u8 id, const struct clk_range *range)
> +{
> +	struct clk_generated *gck;
> +	struct clk *clk = NULL;
> +	struct clk_init_data init;
> +
> +	gck = kzalloc(sizeof(*gck), GFP_KERNEL);
> +	if (!gck)
> +		return ERR_PTR(-ENOMEM);
> +
> +	init.name = name;
> +	init.ops = &generated_ops;
> +	init.parent_names = parent_names;
> +	init.num_parents = num_parents;
> +	init.flags = CLK_SET_RATE_GATE | CLK_SET_PARENT_GATE;
> +
> +	gck->id = id;
> +	gck->hw.init = &init;
> +	gck->pmc = pmc;
> +	gck->range = *range;
> +
> +	clk = clk_register(NULL, &gck->hw);
> +	if (IS_ERR(clk))
> +		kfree(gck);
> +	else
> +		clk_generated_startup(gck);
> +
> +	return clk;
> +}
> +
> +void __init of_sama5d2_clk_generated_setup(struct device_node *np,
> +					   struct at91_pmc *pmc)
> +{
> +	int num;
> +	u32 id;
> +	const char *name;
> +	struct clk *clk;
> +	int num_parents;
> +	const char *parent_names[GENERATED_SOURCE_MAX];
> +	struct device_node *gcknp;
> +	struct clk_range range = CLK_RANGE(0, 0);
> +
> +	num_parents = of_count_phandle_with_args(np, "clocks", "#clock-cells");
> +	if (num_parents <= 0 || num_parents > GENERATED_SOURCE_MAX)
> +		return;
> +
> +	of_clk_parent_fill(np, parent_names, num_parents);
> +
> +	num = of_get_child_count(np);
> +	if (!num || num > PERIPHERAL_MAX)
> +		return;
> +
> +	for_each_child_of_node(np, gcknp) {
> +		if (of_property_read_u32(gcknp, "reg", &id))
> +			continue;
> +
> +		if (id < PERIPHERAL_ID_MIN || id >= PERIPHERAL_MAX)
> +			continue;
> +
> +		if (of_property_read_string(np, "clock-output-names", &name))
> +			name = gcknp->name;
> +
> +		of_at91_get_clk_range(gcknp, "atmel,clk-output-range",
> +				      &range);
> +
> +		clk = at91_clk_register_generated(pmc, name, parent_names,
> +						  num_parents, id, &range);
> +		if (IS_ERR(clk))
> +			continue;
> +
> +		of_clk_add_provider(gcknp, of_clk_src_simple_get, clk);
> +	}
> +}
> diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
> index 39be2be82b0a..3775d82c213d 100644
> --- a/drivers/clk/at91/pmc.c
> +++ b/drivers/clk/at91/pmc.c
> @@ -370,6 +370,12 @@ static const struct of_device_id pmc_clk_ids[] __initconst = {
>  		.data = of_sama5d4_clk_h32mx_setup,
>  	},
>  #endif
> +#if defined(CONFIG_HAVE_AT91_GENERATED_CLK)
> +	{
> +		.compatible = "atmel,sama5d2-clk-generated",
> +		.data = of_sama5d2_clk_generated_setup,
> +	},
> +#endif
>  	{ /*sentinel*/ }
>  };
>  
> diff --git a/drivers/clk/at91/pmc.h b/drivers/clk/at91/pmc.h
> index 8b87771c69b2..f65739272779 100644
> --- a/drivers/clk/at91/pmc.h
> +++ b/drivers/clk/at91/pmc.h
> @@ -118,4 +118,7 @@ void of_at91sam9x5_clk_smd_setup(struct device_node *np,
>  void of_sama5d4_clk_h32mx_setup(struct device_node *np,
>  				struct at91_pmc *pmc);
>  
> +void of_sama5d2_clk_generated_setup(struct device_node *np,
> +				    struct at91_pmc *pmc);
> +
>  #endif /* __PMC_H_ */
> diff --git a/include/linux/clk/at91_pmc.h b/include/linux/clk/at91_pmc.h
> index dfc59e2b64fb..ae61860e6892 100644
> --- a/include/linux/clk/at91_pmc.h
> +++ b/include/linux/clk/at91_pmc.h
> @@ -183,10 +183,17 @@ extern void __iomem *at91_pmc_base;
>  
>  #define AT91_PMC_PCR		0x10c			/* Peripheral Control Register [some SAM9 and SAMA5] */
>  #define		AT91_PMC_PCR_PID_MASK		0x3f
> +#define		AT91_PMC_PCR_GCKCSS_OFFSET	8
> +#define		AT91_PMC_PCR_GCKCSS_MASK	(0x7  << AT91_PMC_PCR_GCKCSS_OFFSET)
> +#define		AT91_PMC_PCR_GCKCSS(n)		((n)  << AT91_PMC_PCR_GCKCSS_OFFSET)	/* GCK Clock Source Selection */
>  #define		AT91_PMC_PCR_CMD		(0x1  <<  12)				/* Command (read=0, write=1) */
>  #define		AT91_PMC_PCR_DIV_OFFSET		16
>  #define		AT91_PMC_PCR_DIV_MASK		(0x3  << AT91_PMC_PCR_DIV_OFFSET)
>  #define		AT91_PMC_PCR_DIV(n)		((n)  << AT91_PMC_PCR_DIV_OFFSET)	/* Divisor Value */
> +#define		AT91_PMC_PCR_GCKDIV_OFFSET	20
> +#define		AT91_PMC_PCR_GCKDIV_MASK	(0xff  << AT91_PMC_PCR_GCKDIV_OFFSET)
> +#define		AT91_PMC_PCR_GCKDIV(n)		((n)  << AT91_PMC_PCR_GCKDIV_OFFSET)	/* Generated Clock Divisor Value */
>  #define		AT91_PMC_PCR_EN			(0x1  <<  28)				/* Enable */
> +#define		AT91_PMC_PCR_GCKEN		(0x1  <<  29)				/* GCK Enable */
>  
>  #endif



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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