linux-kernel - Re: [PATCH 1/7] drm: atmel-hlcdc: add config option for clock selection

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Message-ID: <20190228212558.GB30188@ravnborg.org>
Date:   Thu, 28 Feb 2019 22:25:58 +0100
From:   Sam Ravnborg <sam@...nborg.org>
To:     Claudiu.Beznea@...rochip.com
Cc:     lee.jones@...aro.org, robh+dt@...nel.org, mark.rutland@....com,
        Nicolas.Ferre@...rochip.com, alexandre.belloni@...tlin.com,
        Ludovic.Desroches@...rochip.com, bbrezillon@...nel.org,
        airlied@...ux.ie, daniel@...ll.ch, thierry.reding@...il.com,
        devicetree@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/7] drm: atmel-hlcdc: add config option for clock
 selection

Hi Claudiu

On Wed, Feb 27, 2019 at 04:24:16PM +0000, Claudiu.Beznea@...rochip.com wrote:
> From: Claudiu Beznea <claudiu.beznea@...rochip.com>
> 
> SAM9x60 LCD Controller has no option to select clock source as previous
> controllers have. To be able to use the same driver even for this LCD
> controller add a config option to know if controller supports this.
> 
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> ---
>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c | 12 +++++++-----
>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.h   |  2 ++
>  2 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> index 8070a558d7b1..17a7a18f6a07 100644
> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> @@ -78,7 +78,8 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
>  	unsigned long mode_rate;
>  	struct videomode vm;
>  	unsigned long prate;
> -	unsigned int cfg;
> +	unsigned int mask = ATMEL_HLCDC_CLKDIV_MASK | ATMEL_HLCDC_CLKPOL;
> +	unsigned int cfg = 0;
>  	int div;
Here cfg and mask has initial values.

>  
>  	vm.vfront_porch = adj->crtc_vsync_start - adj->crtc_vdisplay;
> @@ -101,7 +102,10 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
>  		     (adj->crtc_hdisplay - 1) |
>  		     ((adj->crtc_vdisplay - 1) << 16));
>  
> -	cfg = ATMEL_HLCDC_CLKSEL;
> +	if (!crtc->dc->desc->fixed_clksrc) {
> +		cfg = ATMEL_HLCDC_CLKSEL;
> +		mask |= ATMEL_HLCDC_CLKSEL;
> +	}
And here mask is bitwise or with ATMEL_HLCDC_CLKSEL - fine.
But cfg is directly assigned.
If cfg was bitwise or the ATMEL_HLCDC_CLKSEL value then the code was prepared
to have extra flags added above these lines.

Only a small change and no functional difference.

With or without this change:
Reviewed-by: Sam Ravnborg <sam@...nborg.org>