linux-kernel - Re: [PATCH v5 1/3] clk: meson: add emmc sub clock phase delay driver

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Date:   Wed, 24 Oct 2018 18:57:44 +0800
From:   Jianxin Pan <jianxin.pan@...ogic.com>
To:     Jerome Brunet <jbrunet@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>
CC:     Yixun Lan <yixun.lan@...ogic.com>,
        Kevin Hilman <khilman@...libre.com>,
        Carlo Caione <carlo@...one.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Liang Yang <liang.yang@...ogic.com>,
        Jian Hu <jian.hu@...ogic.com>,
        Qiufang Dai <qiufang.dai@...ogic.com>,
        Hanjie Lin <hanjie.lin@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        <linux-clk@...r.kernel.org>, <linux-amlogic@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] clk: meson: add emmc sub clock phase delay driver

On 2018/10/24 16:58, Jerome Brunet wrote:
> On Thu, 2018-10-18 at 13:07 +0800, Jianxin Pan wrote:
>> From: Yixun Lan <yixun.lan@...ogic.com>
[...]
>>
>> --- /dev/null
>> +++ b/drivers/clk/meson/clk-phase-delay.c
>> @@ -0,0 +1,79 @@
>> +// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
>> +/*
>> + * Amlogic Meson MMC Sub Clock Controller Driver
>> + *
>> + * Copyright (c) 2017 Baylibre SAS.
>> + * Author: Jerome Brunet <jbrunet@...libre.com>
>> + *
>> + * Copyright (c) 2018 Amlogic, inc.
>> + * Author: Yixun Lan <yixun.lan@...ogic.com>
>> + */
>> +
>> +#include <linux/clk-provider.h>
>> +#include "clkc.h"
>> +
>> +static int meson_clk_phase_delay_get_phase(struct clk_hw *hw)
>> +{
>> +	struct clk_regmap *clk = to_clk_regmap(hw);
>> +	struct meson_clk_phase_delay_data *ph =
>> +		meson_clk_get_phase_delay_data(clk);
>> +	unsigned long period_ps, p, d;
>> +	int degrees;
>> +	u32 val;
>> +
>> +	regmap_read(clk->map, ph->phase.reg_off, &val);
>> +	p = PARM_GET(ph->phase.width, ph->phase.shift, val);
> 
> there is an helper for this: meson_parm_read()
OK. I will use meson_parm_read instead. Thanks for your review.

The result of regmap_read is shared by two PARM_GETs: phase and delay.
There will be one more register read when change to meson_parm_read, but I don't think it matters.

> 
>> +	degrees = p * 360 / (1 << (ph->phase.width));
>> +
>> +	period_ps = DIV_ROUND_UP((unsigned long)NSEC_PER_SEC * 1000,
>> +				 clk_hw_get_rate(hw));
>> +
>> +	d = PARM_GET(ph->delay.width, ph->delay.shift, val);
>> +	degrees += d * ph->delay_step_ps * 360 / period_ps;
>> +	degrees %= 360;
>> +
>> +	return degrees;
>> +}
>> +
>> +static void meson_clk_apply_phase_delay(struct clk_regmap *clk,
>> +					unsigned int phase,
>> +					unsigned int delay)
> 
> This helper function is a bit overkill.
> simply call meson_parm_write() twice in meson_clk_phase_delay_set_phase().
OK. I will use meson_parm_write() instead.
With meson_parm_write(), there will be one more register read and write
> 
>> +{
>> +	struct meson_clk_phase_delay_data *ph = clk->data;
>> +	u32 val;
>> +
>> +	regmap_read(clk->map, ph->delay.reg_off, &val);
>> +	val = PARM_SET(ph->phase.width, ph->phase.shift, val, phase);
>> +	val = PARM_SET(ph->delay.width, ph->delay.shift, val, delay);
>> +	regmap_write(clk->map, ph->delay.reg_off, val);
>> +}
>> +
>> +static int meson_clk_phase_delay_set_phase(struct clk_hw *hw, int degrees)
>> +{
>> +	struct clk_regmap *clk = to_clk_regmap(hw);
>> +	struct meson_clk_phase_delay_data *ph =
>> +		meson_clk_get_phase_delay_data(clk);
>> +	unsigned long period_ps, d = 0, r;
>> +	u64 p;
>> +
>> +	p = degrees % 360;
>> +	period_ps = DIV_ROUND_UP((unsigned long)NSEC_PER_SEC * 1000,
>> +				 clk_hw_get_rate(hw));
>> +
>> +	/* First compute the phase index (p), the remainder (r) is the
>> +	 * part we'll try to acheive using the delays (d).
>> +	 */
>> +	r = do_div(p, 360 / (1 << (ph->phase.width)));
>> +	d = DIV_ROUND_CLOSEST(r * period_ps,
>> +			      360 * ph->delay_step_ps);
>> +	d = min(d, PMASK(ph->delay.width));
>> +
>> +	meson_clk_apply_phase_delay(clk, p, d);
>> +	return 0;
>> +}
>> +
>> +const struct clk_ops meson_clk_phase_delay_ops = {
>> +	.get_phase = meson_clk_phase_delay_get_phase,
>> +	.set_phase = meson_clk_phase_delay_set_phase,
>> +};
>> +EXPORT_SYMBOL_GPL(meson_clk_phase_delay_ops);
>> diff --git a/drivers/clk/meson/clkc.h b/drivers/clk/meson/clkc.h
>> index 6b96d55..3309d78 100644
>> --- a/drivers/clk/meson/clkc.h
>> +++ b/drivers/clk/meson/clkc.h
>> @@ -105,6 +105,18 @@ struct clk_regmap _name = {						\
>>  	},								\
>>  };
>>  
>> +struct meson_clk_phase_delay_data {
>> +	struct parm			phase;
>> +	struct parm			delay;
>> +	unsigned int			delay_step_ps;
>> +};
>> +
>> +static inline struct meson_clk_phase_delay_data *
>> +meson_clk_get_phase_delay_data(struct clk_regmap *clk)
>> +{
>> +	return (struct meson_clk_phase_delay_data *)clk->data;
>> +}
>> +
>>  /* clk_ops */
>>  extern const struct clk_ops meson_clk_pll_ro_ops;
>>  extern const struct clk_ops meson_clk_pll_ops;
>> @@ -112,5 +124,6 @@ struct clk_regmap _name = {						\
>>  extern const struct clk_ops meson_clk_mpll_ro_ops;
>>  extern const struct clk_ops meson_clk_mpll_ops;
>>  extern const struct clk_ops meson_clk_phase_ops;
>> +extern const struct clk_ops meson_clk_phase_delay_ops;
>>  
>>  #endif /* __CLKC_H */
> 
> 
> .
>