linux-kernel - Re: [PATCH 2/4] pwm: atmel: add support for controllers with 32 bit counters

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Date:   Tue, 19 Feb 2019 08:42:46 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Claudiu.Beznea@...rochip.com
Cc:     thierry.reding@...il.com, robh+dt@...nel.org, mark.rutland@....com,
        Nicolas.Ferre@...rochip.com, alexandre.belloni@...tlin.com,
        Ludovic.Desroches@...rochip.com,
        linux-arm-kernel@...ts.infradead.org, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] pwm: atmel: add support for controllers with 32 bit
 counters

Hello Claudiu,

On Mon, Jan 21, 2019 at 12:30:53PM +0000, Claudiu.Beznea@...rochip.com wrote:
> From: Claudiu Beznea <claudiu.beznea@...rochip.com>
> 
> New SAM9X60's PWM controller use 32 bits counters thus it could generate
> signals with higher period and duty cycles. Update the current driver
> to work with old controller (that uses 16 bits counters) and with the
> new SAM9X60's controller.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
>  drivers/pwm/pwm-atmel.c | 38 +++++++++++++++++++++++++++-----------
>  1 file changed, 27 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
> index 7e86a5266eb6..44f4a1c9f60b 100644
> --- a/drivers/pwm/pwm-atmel.c
> +++ b/drivers/pwm/pwm-atmel.c
> @@ -48,15 +48,15 @@
>  #define PWMV2_CPRD		0x0C
>  #define PWMV2_CPRDUPD		0x10
>  
> -/*
> - * Max value for duty and period
> - *
> - * Although the duty and period register is 32 bit,
> - * however only the LSB 16 bits are significant.
> - */
> -#define PWM_MAX_DTY		0xFFFF
> -#define PWM_MAX_PRD		0xFFFF
> -#define PRD_MAX_PRES		10
> +/* Max values for period and prescaler */
> +
> +/* Only the LSB 16 bits are significant. */
> +#define PWM_MAXV1_PRD		0xFFFF
> +
> +/* All 32 bits are significant. */
> +#define PWM_MAXV2_PRD		0xFFFFFFFF

This symbol is unused, so I wonder if the patch really does what the
commit log promises.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |