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Date: Tue, 14 May 2024 00:25:35 +0300
From: Dmitry Rokosov <ddrokosov@salutedevices.com>
To: Jerome Brunet <jbrunet@baylibre.com>
CC: <neil.armstrong@linaro.org>, <mturquette@baylibre.com>,
	<sboyd@kernel.org>, <robh+dt@kernel.org>,
	<krzysztof.kozlowski+dt@linaro.org>, <khilman@baylibre.com>,
	<martin.blumenstingl@googlemail.com>, <jian.hu@amlogic.com>,
	<kernel@sberdevices.ru>, <rockosov@gmail.com>,
	<linux-amlogic@lists.infradead.org>, <linux-clk@vger.kernel.org>,
	<devicetree@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v2 3/7] clk: meson: a1: pll: support 'syspll'
 general-purpose PLL for CPU clock
Message-ID: <20240513212535.rql55fdrvy2mdsrl@CAB-WSD-L081021>
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 <1jbk59zx4g.fsf@starbuckisacylon.baylibre.com>
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On Mon, May 13, 2024 at 02:48:58PM +0200, Jerome Brunet wrote:
> 
> On Fri 10 May 2024 at 12:08, Dmitry Rokosov <ddrokosov@salutedevices.com> wrote:
> 
> > The 'syspll' PLL, also known as the system PLL, is a general and
> > essential PLL responsible for generating the CPU clock frequency.
> > With its wide-ranging capabilities, it is designed to accommodate
> > frequencies within the range of 768MHz to 1536MHz.
> >
> > Signed-off-by: Dmitry Rokosov <ddrokosov@salutedevices.com>
> > ---
> >  drivers/clk/meson/a1-pll.c | 79 ++++++++++++++++++++++++++++++++++++++
> >  drivers/clk/meson/a1-pll.h |  6 +++
> >  2 files changed, 85 insertions(+)
> >
> > diff --git a/drivers/clk/meson/a1-pll.c b/drivers/clk/meson/a1-pll.c
> > index 60b2e53e7e51..af47ba308bbe 100644
> > --- a/drivers/clk/meson/a1-pll.c
> > +++ b/drivers/clk/meson/a1-pll.c
> > @@ -138,6 +138,82 @@ static struct clk_regmap hifi_pll = {
> >  	},
> >  };
> >  
> > +static const struct pll_mult_range sys_pll_mult_range = {
> > +	.min = 32,
> > +	.max = 64,
> > +};
> > +
> > +static const struct reg_sequence sys_pll_init_regs[] = {
> > +	{ .reg = ANACTRL_SYSPLL_CTRL1, .def = 0x01800000 },
> > +	{ .reg = ANACTRL_SYSPLL_CTRL2, .def = 0x00001100 },
> > +	{ .reg = ANACTRL_SYSPLL_CTRL3, .def = 0x10022300 },
> > +	{ .reg = ANACTRL_SYSPLL_CTRL4, .def = 0x00300000 },
> > +	{ .reg = ANACTRL_SYSPLL_CTRL0, .def = 0x01f18432 },
> > +};
> > +
> > +static struct clk_regmap sys_pll = {
> > +	.data = &(struct meson_clk_pll_data){
> > +		.en = {
> > +			.reg_off = ANACTRL_SYSPLL_CTRL0,
> > +			.shift   = 28,
> > +			.width   = 1,
> > +		},
> > +		.m = {
> > +			.reg_off = ANACTRL_SYSPLL_CTRL0,
> > +			.shift   = 0,
> > +			.width   = 8,
> > +		},
> > +		.n = {
> > +			.reg_off = ANACTRL_SYSPLL_CTRL0,
> > +			.shift   = 10,
> > +			.width   = 5,
> > +		},
> > +		.frac = {
> > +			.reg_off = ANACTRL_SYSPLL_CTRL1,
> > +			.shift   = 0,
> > +			.width   = 19,
> > +		},
> > +		.l = {
> > +			.reg_off = ANACTRL_SYSPLL_STS,
> > +			.shift   = 31,
> > +			.width   = 1,
> > +		},
> > +		.current_en = {
> > +			.reg_off = ANACTRL_SYSPLL_CTRL0,
> > +			.shift   = 26,
> > +			.width   = 1,
> > +		},
> > +		.l_detect = {
> > +			.reg_off = ANACTRL_SYSPLL_CTRL2,
> > +			.shift   = 6,
> > +			.width   = 1,
> > +		},
> > +		.range = &sys_pll_mult_range,
> > +		.init_regs = sys_pll_init_regs,
> > +		.init_count = ARRAY_SIZE(sys_pll_init_regs),
> 
> Like other 'fishy' flags, I would like a clear comment why this flag is
> required so, 2y from now, we will know why it was put there and how we
> can deal with it.
> 

Yep, you are totally correct. The proper comment is required for that.

> > +		.flags = CLK_MESON_PLL_INIT_ONCE,
> > +	},
> > +	.hw.init = &(struct clk_init_data){
> > +		.name = "sys_pll",
> > +		.ops = &meson_clk_pll_ops,
> > +		.parent_names = (const char *[]){ "syspll_in" },
> > +		.num_parents = 1,
> > +	},
> > +};
> > +
> > +static struct clk_fixed_factor sys_pll_div16 = {
> > +	.mult = 1,
> > +	.div = 16,
> > +	.hw.init = &(struct clk_init_data){
> > +		.name = "sys_pll_div16",
> > +		.ops = &clk_fixed_factor_ops,
> > +		.parent_hws = (const struct clk_hw *[]) {
> > +			&sys_pll.hw
> > +		},
> > +		.num_parents = 1,
> > +	},
> > +};
> 
> Unlike the fdivs, this fixed divider is not part of the diagram
> describing the syspll clock.
> 
> IMO, it could as well be in peripheral controller because it exists
> (from what I can see) just testing purposes, to make the sys pll
> observable through tst_out or gen_clk.
> 
> It also looks less awkward in the bindings.
> 

In any case, it is necessary to introduce a new connection. Instead of
using 'sys_pll_div16', it will now be called 'sys_pll'. I agree with you
that this change will make the code more elegant.

> > +
> >  static struct clk_fixed_factor fclk_div2_div = {
> >  	.mult = 1,
> >  	.div = 2,
> > @@ -283,6 +359,8 @@ static struct clk_hw *a1_pll_hw_clks[] = {
> >  	[CLKID_FCLK_DIV5]	= &fclk_div5.hw,
> >  	[CLKID_FCLK_DIV7]	= &fclk_div7.hw,
> >  	[CLKID_HIFI_PLL]	= &hifi_pll.hw,
> > +	[CLKID_SYS_PLL]		= &sys_pll.hw,
> > +	[CLKID_SYS_PLL_DIV16]	= &sys_pll_div16.hw,
> >  };
> >  
> >  static struct clk_regmap *const a1_pll_regmaps[] = {
> > @@ -293,6 +371,7 @@ static struct clk_regmap *const a1_pll_regmaps[] = {
> >  	&fclk_div5,
> >  	&fclk_div7,
> >  	&hifi_pll,
> > +	&sys_pll,
> >  };
> >  
> >  static struct regmap_config a1_pll_regmap_cfg = {
> > diff --git a/drivers/clk/meson/a1-pll.h b/drivers/clk/meson/a1-pll.h
> > index 4be17b2bf383..666d9b2137e9 100644
> > --- a/drivers/clk/meson/a1-pll.h
> > +++ b/drivers/clk/meson/a1-pll.h
> > @@ -18,6 +18,12 @@
> >  #define ANACTRL_FIXPLL_CTRL0	0x0
> >  #define ANACTRL_FIXPLL_CTRL1	0x4
> >  #define ANACTRL_FIXPLL_STS	0x14
> > +#define ANACTRL_SYSPLL_CTRL0	0x80
> > +#define ANACTRL_SYSPLL_CTRL1	0x84
> > +#define ANACTRL_SYSPLL_CTRL2	0x88
> > +#define ANACTRL_SYSPLL_CTRL3	0x8c
> > +#define ANACTRL_SYSPLL_CTRL4	0x90
> > +#define ANACTRL_SYSPLL_STS	0x94
> >  #define ANACTRL_HIFIPLL_CTRL0	0xc0
> >  #define ANACTRL_HIFIPLL_CTRL1	0xc4
> >  #define ANACTRL_HIFIPLL_CTRL2	0xc8
> 
> 
> -- 
> Jerome

-- 
Thank you,
Dmitry