linux-kernel - Re: [PATCH v3 5/6] drm: atmel-hlcdc: prefer a lower pixel-clock than requested

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Date:   Thu, 2 Jan 2020 10:08:48 +0100
From:   Sam Ravnborg <sam@...nborg.org>
To:     Claudiu Beznea <claudiu.beznea@...rochip.com>
Cc:     boris.brezillon@...tlin.com, airlied@...ux.ie,
        nicolas.ferre@...rochip.com, alexandre.belloni@...tlin.com,
        lee.jones@...aro.org, peda@...ntia.se,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/6] drm: atmel-hlcdc: prefer a lower pixel-clock than
 requested

On Wed, Dec 18, 2019 at 02:28:28PM +0200, Claudiu Beznea wrote:
> From: Peter Rosin <peda@...ntia.se>
> 
> The intention was to only select a higher pixel-clock rate than the
> requested, if a slight overclocking would result in a rate significantly
> closer to the requested rate than if the conservative lower pixel-clock
> rate is selected. The fixed patch has the logic the other way around and
> actually prefers the higher frequency. Fix that.
> 
> Fixes: f6f7ad323461 ("drm/atmel-hlcdc: allow selecting a higher pixel-clock than requested")
The id is wrong here - the right one is: 9946a3a9dbedaaacef8b7e94f6ac144f1daaf1de
The wrong id above was used before - so I think it is a copy'n'paste
thing.

Hint: try "dim fixes 9946a3a9dbedaaacef8b7e94f6ac144f1daaf1de"

If I get a quick response from Lee I can fix it up while applying.

	Sam

> Reported-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> Tested-by: Claudiu Beznea <claudiu.beznea@...rochip.com>
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> index 721fa88bf71d..10985134ce0b 100644
> --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
> @@ -121,8 +121,8 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
>  		int div_low = prate / mode_rate;
>  
>  		if (div_low >= 2 &&
> -		    ((prate / div_low - mode_rate) <
> -		     10 * (mode_rate - prate / div)))
> +		    (10 * (prate / div_low - mode_rate) <
> +		     (mode_rate - prate / div)))
>  			/*
>  			 * At least 10 times better when using a higher
>  			 * frequency than requested, instead of a lower.
> -- 
> 2.7.4