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Date:	Mon, 22 Sep 2014 10:51:55 +0200
From:	Boris BREZILLON <boris.brezillon@...e-electrons.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 1/7] clk: at91: add a driver for the h32mx clock

Hi Alexandre,

Sorry for the late reply.

On Mon, 15 Sep 2014 18:15:53 +0200
Alexandre Belloni <alexandre.belloni@...e-electrons.com> wrote:

> Newer SoCs have two different AHB interconnect. The AHB 32 bits Matrix
> interconnect (h32mx) has a clock that can be setup at the half of the h64mx
> clock (which is mck). The h32mx clock can not exceed 90 MHz.

You'll find some comments below, but none of them should really impact
the SoC (AFAIU we never set the h32mx clk rate within the kernel and
rely on the bootstrap configuration), hence here is my

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

> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> ---
> Cc:Mike Turquette <mturquette@...aro.org>
> 
>  .../devicetree/bindings/clock/at91-clock.txt       |  15 +++
>  arch/arm/mach-at91/Kconfig                         |   3 +
>  drivers/clk/at91/Makefile                          |   1 +
>  drivers/clk/at91/clk-h32mx.c                       | 123 +++++++++++++++++++++
>  drivers/clk/at91/pmc.c                             |   6 +
>  drivers/clk/at91/pmc.h                             |   5 +
>  include/linux/clk/at91_pmc.h                       |   1 +
>  7 files changed, 154 insertions(+)
>  create mode 100644 drivers/clk/at91/clk-h32mx.c
> 
> diff --git a/Documentation/devicetree/bindings/clock/at91-clock.txt b/Documentation/devicetree/bindings/clock/at91-clock.txt
> index b3d544ca522a..40dc2405de7c 100644
> --- a/Documentation/devicetree/bindings/clock/at91-clock.txt
> +++ b/Documentation/devicetree/bindings/clock/at91-clock.txt
> @@ -74,6 +74,9 @@ Required properties:
>  	"atmel,at91sam9x5-clk-utmi":
>  		at91 utmi clock
>  
> +	"atmel,sama5d4-clk-h32mx":
> +		at91 h32mx 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).
> @@ -447,3 +450,15 @@ For example:
>  		#clock-cells = <0>;
>  		clocks = <&main>;
>  	};
> +
> +Required properties for 32 bits bus Matrix clock (h32mx clock):
> +- #clock-cells : from common clock binding; shall be set to 0.
> +- clocks : shall be the master clock source phandle.
> +
> +For example:
> +	h32ck: h32mxck {
> +		#clock-cells = <0>;
> +		compatible = "atmel,sama5d4-clk-h32mx";
> +		clocks = <&mck>;
> +	};
> +
> diff --git a/arch/arm/mach-at91/Kconfig b/arch/arm/mach-at91/Kconfig
> index 6eb3c658761d..fd177956dd56 100644
> --- a/arch/arm/mach-at91/Kconfig
> +++ b/arch/arm/mach-at91/Kconfig
> @@ -39,6 +39,9 @@ config AT91_SAM9_TIME
>  config HAVE_AT91_SMD
>  	bool
>  
> +config HAVE_AT91_H32MX
> +	bool
> +
>  config SOC_AT91SAM9
>  	bool
>  	select AT91_SAM9_TIME
> diff --git a/drivers/clk/at91/Makefile b/drivers/clk/at91/Makefile
> index 4998aee59267..89a48a7bd5df 100644
> --- a/drivers/clk/at91/Makefile
> +++ b/drivers/clk/at91/Makefile
> @@ -9,3 +9,4 @@ obj-y += clk-system.o clk-peripheral.o clk-programmable.o
>  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
> diff --git a/drivers/clk/at91/clk-h32mx.c b/drivers/clk/at91/clk-h32mx.c
> new file mode 100644
> index 000000000000..152dcb3f7b5f
> --- /dev/null
> +++ b/drivers/clk/at91/clk-h32mx.c
> @@ -0,0 +1,123 @@
> +/*
> + * clk-h32mx.c
> + *
> + *  Copyright (C) 2014 Atmel
> + *
> + * Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> + *
> + * 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/delay.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/io.h>
> +#include <linux/interrupt.h>
> +#include <linux/irq.h>
> +#include <linux/sched.h>
> +#include <linux/wait.h>
> +
> +#include "pmc.h"
> +
> +#define H32MX_MAX_FREQ	90000000
> +
> +struct clk_sama5d4_h32mx {
> +	struct clk_hw hw;
> +	struct at91_pmc *pmc;
> +};
> +
> +#define to_clk_sama5d4_h32mx(hw) container_of(hw, struct clk_sama5d4_h32mx, hw)
> +
> +static unsigned long clk_sama5d4_h32mx_recalc_rate(struct clk_hw *hw,
> +						 unsigned long parent_rate)
> +{
> +	struct clk_sama5d4_h32mx *h32mxclk = to_clk_sama5d4_h32mx(hw);
> +
> +	if (pmc_read(h32mxclk->pmc, AT91_PMC_MCKR) & AT91_PMC_H32MXDIV)
> +		return parent_rate / 2;
> +
> +	if (parent_rate > H32MX_MAX_FREQ)
> +		pr_warn("H32MX clock is too fast\n");

I would check for this even if we apply a divider to the clk:

	unsigned long rate;

	if (pmc_read(h32mxclk->pmc, AT91_PMC_MCKR) & AT91_PMC_H32MXDIV)
		rate = parent_rate / 2;
	else
		rate = parent_rate;

	if (rate > H32MX_MAX_FREQ)
		pr_warn("H32MX clock is too fast\n");

	return rate;

> +	return parent_rate;
> +}
> +
> +static long clk_sama5d4_h32mx_round_rate(struct clk_hw *hw, unsigned long rate,
> +				       unsigned long *parent_rate)
> +{
> +	unsigned long div;
> +

How about checking if the requested rate is below the maximum rate
(H32MX_MAX_FREQ), and returning -EINVAL if this is not the case ?

> +	if (rate > *parent_rate)
> +		return *parent_rate;
> +	div = *parent_rate / 2;
> +	if (rate < div)
> +		return div;
> +
> +	if (rate - div < *parent_rate - rate)
> +		return div;

Do we really want to find the closest rate for this clk ? Isn't a floor
rate more appropriate in this case ?

I'll let Nicolas decide :-).

> +
> +	return *parent_rate;
> +}
> +
> +static int clk_sama5d4_h32mx_set_rate(struct clk_hw *hw, unsigned long rate,
> +				    unsigned long parent_rate)
> +{
> +	struct clk_sama5d4_h32mx *h32mxclk = to_clk_sama5d4_h32mx(hw);
> +	struct at91_pmc *pmc = h32mxclk->pmc;
> +	u32 tmp;
> +
> +	if (parent_rate != rate && (parent_rate / 2) != rate)
> +		return -EINVAL;
> +
> +	pmc_lock(pmc);
> +	tmp = pmc_read(pmc, AT91_PMC_MCKR) & ~AT91_PMC_H32MXDIV;
> +	if ((parent_rate / 2) == rate)
> +		tmp |= AT91_PMC_H32MXDIV;
> +	pmc_write(pmc, AT91_PMC_MCKR, tmp);
> +	pmc_unlock(pmc);
> +
> +	return 0;
> +}
> +
> +static const struct clk_ops h32mx_ops = {
> +	.recalc_rate = clk_sama5d4_h32mx_recalc_rate,
> +	.round_rate = clk_sama5d4_h32mx_round_rate,
> +	.set_rate = clk_sama5d4_h32mx_set_rate,
> +};
> +
> +void __init of_sama5d4_clk_h32mx_setup(struct device_node *np,
> +				     struct at91_pmc *pmc)
> +{
> +	struct clk_sama5d4_h32mx *h32mxclk;
> +	struct clk_init_data init;
> +	const char *parent_name;
> +	struct clk *clk;
> +
> +	h32mxclk = kzalloc(sizeof(*h32mxclk), GFP_KERNEL);
> +	if (!h32mxclk)
> +		return;
> +
> +	parent_name = of_clk_get_parent_name(np, 0);
> +
> +	init.name = np->name;
> +	init.ops = &h32mx_ops;
> +	init.parent_names = parent_name ? &parent_name : NULL;
> +	init.num_parents = parent_name ? 1 : 0;
> +	init.flags = CLK_SET_RATE_GATE;
> +
> +	h32mxclk->hw.init = &init;
> +	h32mxclk->pmc = pmc;
> +
> +	clk = clk_register(NULL, &h32mxclk->hw);
> +	if (!clk)
> +		return;
> +
> +	of_clk_add_provider(np, of_clk_src_simple_get, clk);
> +}
> diff --git a/drivers/clk/at91/pmc.c b/drivers/clk/at91/pmc.c
> index 524196bb35a5..386999b4f8eb 100644
> --- a/drivers/clk/at91/pmc.c
> +++ b/drivers/clk/at91/pmc.c
> @@ -337,6 +337,12 @@ static const struct of_device_id pmc_clk_ids[] __initconst = {
>  		.data = of_at91sam9x5_clk_smd_setup,
>  	},
>  #endif
> +#if defined(CONFIG_HAVE_AT91_H32MX)
> +	{
> +		.compatible = "atmel,sama5d4-clk-h32mx",
> +		.data = of_sama5d4_clk_h32mx_setup,
> +	},
> +#endif
>  	{ /*sentinel*/ }
>  };
>  
> diff --git a/drivers/clk/at91/pmc.h b/drivers/clk/at91/pmc.h
> index 6c7625976113..52d2041fa3f6 100644
> --- a/drivers/clk/at91/pmc.h
> +++ b/drivers/clk/at91/pmc.h
> @@ -120,4 +120,9 @@ extern void __init of_at91sam9x5_clk_smd_setup(struct device_node *np,
>  					       struct at91_pmc *pmc);
>  #endif
>  
> +#if defined(CONFIG_HAVE_AT91_SMD)
> +extern void __init of_sama5d4_clk_h32mx_setup(struct device_node *np,
> +					      struct at91_pmc *pmc);
> +#endif
> +
>  #endif /* __PMC_H_ */
> diff --git a/include/linux/clk/at91_pmc.h b/include/linux/clk/at91_pmc.h
> index de4268d4987a..c8e3b3d1eded 100644
> --- a/include/linux/clk/at91_pmc.h
> +++ b/include/linux/clk/at91_pmc.h
> @@ -125,6 +125,7 @@ extern void __iomem *at91_pmc_base;
>  #define		AT91_PMC_PLLADIV2	(1 << 12)		/* PLLA divisor by 2 [some SAM9 only] */
>  #define			AT91_PMC_PLLADIV2_OFF		(0 << 12)
>  #define			AT91_PMC_PLLADIV2_ON		(1 << 12)
> +#define		AT91_PMC_H32MXDIV	BIT(24)
>  
>  #define	AT91_PMC_USB		0x38			/* USB Clock Register [some SAM9 only] */
>  #define		AT91_PMC_USBS		(0x1 <<  0)		/* USB OHCI Input clock selection */



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