linux-kernel - Re: [PATCH 03/14] pwm: meson: use GENMASK and FIELD

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Date:   Mon, 27 May 2019 14:25:44 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org, linux-pwm@...r.kernel.org,
        thierry.reding@...il.com, u.kleine-koenig@...gutronix.de
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 03/14] pwm: meson: use GENMASK and FIELD_PREP for the lo
 and hi values

On 25/05/2019 20:11, Martin Blumenstingl wrote:
> meson_pwm_calc() ensures that "lo" is always less than 16 bits wide
> (otherwise it would overflow into the "hi" part of the REG_PWM_{A,B}
> register).
> Use GENMASK and FIELD_PREP for the lo and hi values to make it easier to
> spot how wide these are internally. Additionally this is a preparation
> step for the .get_state() implementation where the GENMASK() for lo and
> hi becomes handy because it can be used with FIELD_GET() to extract the
> values from the register REG_PWM_{A,B} register.
> 
> No functional changes intended.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
>  drivers/pwm/pwm-meson.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
> index 35b38c7201c3..c62a3ac924d0 100644
> --- a/drivers/pwm/pwm-meson.c
> +++ b/drivers/pwm/pwm-meson.c
> @@ -5,6 +5,8 @@
>   * Copyright (C) 2014 Amlogic, Inc.
>   */
>  
> +#include <linux/bitfield.h>
> +#include <linux/bits.h>
>  #include <linux/clk.h>
>  #include <linux/clk-provider.h>
>  #include <linux/err.h>
> @@ -20,7 +22,8 @@
>  
>  #define REG_PWM_A		0x0
>  #define REG_PWM_B		0x4
> -#define PWM_HIGH_SHIFT		16
> +#define PWM_LOW_MASK		GENMASK(15, 0)
> +#define PWM_HIGH_MASK		GENMASK(31, 16)
>  
>  #define REG_MISC_AB		0x8
>  #define MISC_B_CLK_EN		BIT(23)
> @@ -217,7 +220,8 @@ static void meson_pwm_enable(struct meson_pwm *meson, struct pwm_device *pwm)
>  	value |= clk_enable;
>  	writel(value, meson->base + REG_MISC_AB);
>  
> -	value = (channel->hi << PWM_HIGH_SHIFT) | channel->lo;
> +	value = FIELD_PREP(PWM_HIGH_MASK, channel->hi) |
> +		FIELD_PREP(PWM_LOW_MASK, channel->lo);
>  	writel(value, meson->base + offset);
>  
>  	value = readl(meson->base + REG_MISC_AB);
> 

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>