linux-kernel - Re: [PATCH 1/2] drm/arm/hdlcd: Actually validate CRTC modes

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Date:   Tue, 4 Jun 2019 15:20:46 +0100
From:   Liviu Dudau <liviu.dudau@....com>
To:     Robin Murphy <robin.murphy@....com>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm/arm/hdlcd: Actually validate CRTC modes

On Fri, May 17, 2019 at 05:37:21PM +0100, Robin Murphy wrote:
> Rather than allowing any old mode through, then subsequently refusing
> unmatchable clock rates in atomic_check when it's too late to back out
> and pick a different mode, let's do that validation up-front where it
> will cause unsupported modes to be correctly pruned in the first place.
> 
> This also eliminates an issue whereby a perceived clock rate of 0 would
> cause atomic disable to fail and prevent the module from being unloaded.
> 
> Signed-off-by: Robin Murphy <robin.murphy@....com>

Acked-by: Liviu Dudau <liviu.dudau@....com>

Thanks for the patch!

Best regards,
Liviu

> ---
> 
> This supersedes my previous patch here:
> https://patchwork.freedesktop.org/patch/288553/
> ---
>  drivers/gpu/drm/arm/hdlcd_crtc.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
> index 0b2b62f8fa3c..ecac6fe0b213 100644
> --- a/drivers/gpu/drm/arm/hdlcd_crtc.c
> +++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
> @@ -186,20 +186,19 @@ static void hdlcd_crtc_atomic_disable(struct drm_crtc *crtc,
>  	clk_disable_unprepare(hdlcd->clk);
>  }
>  
> -static int hdlcd_crtc_atomic_check(struct drm_crtc *crtc,
> -				   struct drm_crtc_state *state)
> +static enum drm_mode_status hdlcd_crtc_mode_valid(struct drm_crtc *crtc,
> +		const struct drm_display_mode *mode)
>  {
>  	struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
> -	struct drm_display_mode *mode = &state->adjusted_mode;
>  	long rate, clk_rate = mode->clock * 1000;
>  
>  	rate = clk_round_rate(hdlcd->clk, clk_rate);
>  	if (rate != clk_rate) {
>  		/* clock required by mode not supported by hardware */
> -		return -EINVAL;
> +		return MODE_NOCLOCK;
>  	}
>  
> -	return 0;
> +	return MODE_OK;
>  }
>  
>  static void hdlcd_crtc_atomic_begin(struct drm_crtc *crtc,
> @@ -220,7 +219,7 @@ static void hdlcd_crtc_atomic_begin(struct drm_crtc *crtc,
>  }
>  
>  static const struct drm_crtc_helper_funcs hdlcd_crtc_helper_funcs = {
> -	.atomic_check	= hdlcd_crtc_atomic_check,
> +	.mode_valid	= hdlcd_crtc_mode_valid,
>  	.atomic_begin	= hdlcd_crtc_atomic_begin,
>  	.atomic_enable	= hdlcd_crtc_atomic_enable,
>  	.atomic_disable	= hdlcd_crtc_atomic_disable,
> -- 
> 2.21.0.dirty
> 

-- 
====================
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| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
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