Date:	Fri, 21 Mar 2014 13:49:32 +0100
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Mike Turquette <mturquette@...aro.org>
CC:	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>
Subject: Re: [PATCH 1/5] clk: berlin: add support for berlin plls

On 03/21/2014 12:43 PM, Alexandre Belloni wrote:
> This drivers allows to provide DT clocks for the cpu and system PLLs found on
> Marvell Berlin SoCs.
>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
> ---
>   drivers/clk/Makefile              |   1 +
>   drivers/clk/berlin/Makefile       |   1 +
>   drivers/clk/berlin/clk.h          |  35 +++++++++++++
>   drivers/clk/berlin/pll-berlin2.c  |  41 ++++++++++++++++
>   drivers/clk/berlin/pll-berlin2q.c |  41 ++++++++++++++++
>   drivers/clk/berlin/pll.c          | 100 ++++++++++++++++++++++++++++++++++++++
>   6 files changed, 219 insertions(+)
>   create mode 100644 drivers/clk/berlin/Makefile
>   create mode 100644 drivers/clk/berlin/clk.h
>   create mode 100644 drivers/clk/berlin/pll-berlin2.c
>   create mode 100644 drivers/clk/berlin/pll-berlin2q.c
>   create mode 100644 drivers/clk/berlin/pll.c
>
> diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
> index a367a9831717..4a2602737c27 100644
> --- a/drivers/clk/Makefile
> +++ b/drivers/clk/Makefile
> @@ -29,6 +29,7 @@ obj-$(CONFIG_ARCH_VT8500)		+= clk-vt8500.o
>   obj-$(CONFIG_COMMON_CLK_WM831X)		+= clk-wm831x.o
>   obj-$(CONFIG_COMMON_CLK_XGENE)		+= clk-xgene.o
>   obj-$(CONFIG_COMMON_CLK_AT91)		+= at91/
> +obj-$(CONFIG_ARCH_BERLIN)		+= berlin/
>   obj-$(CONFIG_ARCH_HI3xxx)		+= hisilicon/
>   obj-$(CONFIG_COMMON_CLK_KEYSTONE)	+= keystone/

I'll have a look at clk/Makefile later myself, but alphabetic ordering
seems to be broken by ARCH_HI3xxx already. Anyway, we shouldn't just
add another violator.

>   ifeq ($(CONFIG_COMMON_CLK), y)
> diff --git a/drivers/clk/berlin/Makefile b/drivers/clk/berlin/Makefile
> new file mode 100644
> index 000000000000..4f6580e2a3ee
> --- /dev/null
> +++ b/drivers/clk/berlin/Makefile
> @@ -0,0 +1 @@
> +obj-y += pll.o pll-berlin2.o pll-berlin2q.o

obj-y += pll.o
obj-$(CONFIG_MACH_BERLIN_BG2)	+= pll-berlin2.o
obj-$(CONFIG_MACH_BERLIN_BG2CD)	+= pll-berlin2.o
obj-$(CONFIG_MACH_BERLIN_BG2Q)	+= pll-berlin2q.o

Which reminds me, that we forgot to add MACH_BERLIN_BG2Q to
arch/arm/mach-berlin/Kconfig. Can you spin a patch?

> diff --git a/drivers/clk/berlin/clk.h b/drivers/clk/berlin/clk.h

I prefer to have this include named "common.h" as I guess we will
dump all common declarations in here.

> new file mode 100644
> index 000000000000..41459db31a02
> --- /dev/null
> +++ b/drivers/clk/berlin/clk.h
> @@ -0,0 +1,35 @@
> +/*
> + * Copyright (c) 2013 Marvell Technology Group Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef __BERLIN_CLK_H
> +#define __BERLIN_CLK_H
> +
> +#include <linux/clk-provider.h>

What is this include good for in here?

You will need struct device_node declared, but a simple

struct device_node;

should be sufficient.

> +struct berlin_pllmap {
> +	const u8	*vcodiv;
> +	u32		fbdiv_mask;
> +	u32		rfdiv_mask;
> +	u32		divsel_mask;
> +	u8		fbdiv_shift;
> +	u8		rfdiv_shift;
> +	u8		divsel_shift;
> +	u8		mult;
> +};
> +
> +extern void __init berlin_pll_setup(struct device_node *np,
> +				struct berlin_pllmap *map);
> +
> +#endif /* BERLIN_CLK_H */
> diff --git a/drivers/clk/berlin/pll-berlin2.c b/drivers/clk/berlin/pll-berlin2.c
> new file mode 100644
> index 000000000000..5f5b4674f811
> --- /dev/null
> +++ b/drivers/clk/berlin/pll-berlin2.c
> @@ -0,0 +1,41 @@
> +/*
> + * Copyright (c) 2014 Marvell Technology Group Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/kernel.h>
> +#include <linux/clk-provider.h>

Please sort includes alphabetically, it will save us some pain
in the future.

> +#include "clk.h"

#include "common.h"

> +static const u8 vcodiv_berlin2[] = {10, 15, 20, 25, 30, 40, 50, 60, 80};
> +
> +static struct berlin_pllmap berlin_pll_map = {
> +	.vcodiv = vcodiv_berlin2,
> +	.fbdiv_mask = 0x1FF,
> +	.rfdiv_mask = 0x1F,
> +	.divsel_mask = 0xF,

divsel_mask allows 16 possible values, vcodiv_berlin2[] only provides
9, and common pll driver below does not know how many valid vcodiv
values are passed. That can become dangerous..

I'd rather extend vcodiv_berlin2 to full divsel range and provide
safe (=1) divisiors. This way wrong/new register values will only
break clock frequency derived.

> +	.fbdiv_shift = 6,
> +	.rfdiv_shift = 1,
> +	.divsel_shift = 7,

Have .foo_mask and .foo_shift together?

> +	.mult = 10,
> +};
> +
> +static void __init berlin2_pll_setup(struct device_node *np)
> +{
> +	berlin_pll_setup(np, &berlin_pll_map);
> +}
> +CLK_OF_DECLARE(berlin2q_pll, "marvell,berlin2-pll", berlin2_pll_setup);
> +
> diff --git a/drivers/clk/berlin/pll-berlin2q.c b/drivers/clk/berlin/pll-berlin2q.c
> new file mode 100644
> index 000000000000..8ddfa69cf8c4
> --- /dev/null
> +++ b/drivers/clk/berlin/pll-berlin2q.c
> @@ -0,0 +1,41 @@
> +/*
> + * Copyright (c) 2013 Marvell Technology Group Ltd.

nit: 2014?

> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/kernel.h>
> +#include <linux/clk-provider.h>

same as above.

> +#include "clk.h"

ditto.

> +static const u8 vcodiv_berlin2q[] = {1, 0, 2, 0, 3, 4, 0, 6, 8};
> +
> +static struct berlin_pllmap berlin2q_pll_map = {
> +	.vcodiv = vcodiv_berlin2q,
> +	.fbdiv_mask = 0x1FF,
> +	.rfdiv_mask = 0x1F,
> +	.divsel_mask = 0xF,
> +	.fbdiv_shift = 7,
> +	.rfdiv_shift = 2,
> +	.divsel_shift = 9,
> +	.mult = 1,
> +};

ditto.

> +static void __init berlin2q_pll_setup(struct device_node *np)
> +{
> +	berlin_pll_setup(np, &berlin2q_pll_map);
> +}
> +CLK_OF_DECLARE(berlin2q_pll, "marvell,berlin2q-pll", berlin2q_pll_setup);
> +
> diff --git a/drivers/clk/berlin/pll.c b/drivers/clk/berlin/pll.c
> new file mode 100644
> index 000000000000..188b385af436
> --- /dev/null
> +++ b/drivers/clk/berlin/pll.c
> @@ -0,0 +1,100 @@
> +/*
> + * Copyright (c) 2013 Marvell Technology Group Ltd.

nit: 2014?

> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/slab.h>
> +#include <linux/kernel.h>
> +#include <linux/clk-provider.h>

same as above.

> +#include "clk.h"

ditto.

> +struct berlin_pll {
> +	struct clk_hw	hw;
> +	void __iomem	*base;
> +	void		*data;

struct berlin2_pllmap *map instead?

> +};
> +
> +#define to_berlin_pll(hw)	container_of(hw, struct berlin_pll, hw)
> +
> +#define PLL_CTRL0	0x00
> +#define PLL_CTRL1	0x04
> +
> +static inline u32 berlin_pll_read(struct berlin_pll *pll, unsigned long offset)
> +{
> +	return readl_relaxed(pll->base + offset);
> +}
> +
> +static unsigned long berlin_pll_recalc_rate(struct clk_hw *hw,
> +					unsigned long parent_rate)

Maybe have a nice little comment on how pll output frequency is
calculated out of the 5 variables?

> +{
> +	struct berlin_pll *pll = to_berlin_pll(hw);
> +	struct berlin_pllmap *map = pll->data;
> +	u32 val, fbdiv, rfdiv, vcodivsel;
> +
> +	val = berlin_pll_read(pll, PLL_CTRL0);
> +	fbdiv = (val >> map->fbdiv_shift) & map->fbdiv_mask;
> +	rfdiv = (val >> map->rfdiv_shift) & map->rfdiv_mask;
> +	if (rfdiv == 0)
> +		rfdiv = 1;
> +
> +	val = berlin_pll_read(pll, PLL_CTRL1);
> +	vcodivsel = (val >> map->divsel_shift) & map->divsel_mask;
> +
> +	return parent_rate * fbdiv * map->mult / rfdiv /
> +		map->vcodiv[vcodivsel];

IMHO

parent_rate *= fbdiv * map->mult;
parent_rate /= rfdiv;
return parent_rate / map->vcodiv[vcodivsel];

makes it slightly more readable, but that is up to you.

> +}
> +
> +static const struct clk_ops berlin_pll_ops = {
> +	.recalc_rate	= berlin_pll_recalc_rate,
> +};
> +
> +void __init berlin_pll_setup(struct device_node *np,
> +			struct berlin_pllmap *map)
> +{
> +	struct clk_init_data init;
> +	struct berlin_pll *pll;
> +	const char *parent_name;
> +	struct clk *clk;
> +	int ret;
> +
> +	pll = kzalloc(sizeof(*pll), GFP_KERNEL);
> +	if (WARN_ON(!pll))
> +		return;
> +
> +	pll->base = of_iomap(np, 0);
> +	if (WARN_ON(!pll->base))
> +		return;
> +
> +	pll->data = map;

pll->map = map;

> +
> +	init.name = np->name;
> +	init.ops = &berlin_pll_ops;
> +	parent_name = of_clk_get_parent_name(np, 0);
> +	init.parent_names = &parent_name;
> +	init.num_parents = 1;
> +
> +	pll->hw.init = &init;
> +
> +	clk = clk_register(NULL, &pll->hw);
> +	if (WARN_ON(IS_ERR(clk)))
> +		return;
> +
> +	ret = of_clk_add_provider(np, of_clk_src_simple_get, clk);
> +	if (WARN_ON(ret))
> +		return;
> +}
> +
>

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