linux-kernel - Re: [PATCH v2 8/8] drm: arc: Use crtc->mode

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Message-ID: <48215037.0gN33EkSK6@avalon>
Date:   Fri, 12 May 2017 12:57:30 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Jose Abreu <Jose.Abreu@...opsys.com>, linux-kernel@...r.kernel.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        Carlos Palminha <CARLOS.PALMINHA@...opsys.com>
Subject: Re: [PATCH v2 8/8] drm: arc: Use crtc->mode_valid() callback

Hi Jose,

Thank you for the patch.

On Tuesday 09 May 2017 18:00:15 Jose Abreu wrote:
> Now that we have a callback to check if crtc supports a given mode
> we can use it in arcpgu so that we restrict the number of probbed
> modes to the ones we can actually display.
> 
> This is specially useful because arcpgu crtc is responsible to set
> a clock value in the commit() stage but unfortunatelly this clock
> does not support all the needed ranges.
> 
> Also, remove the atomic_check() callback as mode_valid() callback
> will be called before.
> 
> Signed-off-by: Jose Abreu <joabreu@...opsys.com>
> Cc: Carlos Palminha <palminha@...opsys.com>
> Cc: Alexey Brodkin <abrodkin@...opsys.com>
> Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@...ll.ch>
> Cc: Dave Airlie <airlied@...ux.ie>
> Cc: Andrzej Hajda <a.hajda@...sung.com>
> Cc: Archit Taneja <architt@...eaurora.org>
> ---
>  drivers/gpu/drm/arc/arcpgu_crtc.c | 39 ++++++++++++++++++++---------------
>  1 file changed, 24 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arc/arcpgu_crtc.c
> b/drivers/gpu/drm/arc/arcpgu_crtc.c index ad9a959..01cae0a 100644
> --- a/drivers/gpu/drm/arc/arcpgu_crtc.c
> +++ b/drivers/gpu/drm/arc/arcpgu_crtc.c
> @@ -32,6 +32,18 @@
>  	{ "r8g8b8", 24, {16, 8}, {8, 8}, {0, 8}, {0, 0}, DRM_FORMAT_RGB888 },
>  };
> 
> +static bool arc_pgu_is_mode_valid(struct arcpgu_drm_private *arcpgu,
> +				  const struct drm_display_mode *mode)
> +{
> +	long rate, clk_rate = mode->clock * 1000;
> +
> +	rate = clk_round_rate(arcpgu->clk, clk_rate);
> +	if (rate != clk_rate)
> +		return false;

This isn't anything new introduced by this patch, but shouldn't drivers allow 
for some margin in clock frequencies ? Surely if the mode requires a 
60.000.000 Hz frequency and the hardware can only generate 59.999.999 Hz or 
60.000.001 Hz we shouldn't fail. As far as I understand, this is something the 
mode_fixup() operation is supposed to handle, but the arc driver doesn't 
implement it.

> +	return true;
> +}

Can't you inline this in arc_pgu_crtc_mode_valid() as there's a single caller 
?

>  static void arc_pgu_set_pxl_fmt(struct drm_crtc *crtc)
>  {
>  	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
> @@ -64,6 +76,17 @@ static void arc_pgu_set_pxl_fmt(struct drm_crtc *crtc)
>  	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
>  };
> 
> +enum drm_mode_status arc_pgu_crtc_mode_valid(struct drm_crtc *crtc,
> +					     const struct drm_display_mode 
*mode)
> +{
> +	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
> +
> +	if (!arc_pgu_is_mode_valid(arcpgu, mode))
> +		return MODE_NOCLOCK;
> +
> +	return MODE_OK;
> +}
> +
>  static void arc_pgu_crtc_mode_set_nofb(struct drm_crtc *crtc)
>  {
>  	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
> @@ -129,20 +152,6 @@ static void arc_pgu_crtc_disable(struct drm_crtc *crtc)
> ~ARCPGU_CTRL_ENABLE_MASK);
>  }
> 
> -static int arc_pgu_crtc_atomic_check(struct drm_crtc *crtc,
> -				     struct drm_crtc_state *state)
> -{
> -	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
> -	struct drm_display_mode *mode = &state->adjusted_mode;
> -	long rate, clk_rate = mode->clock * 1000;
> -
> -	rate = clk_round_rate(arcpgu->clk, clk_rate);
> -	if (rate != clk_rate)
> -		return -EINVAL;
> -
> -	return 0;
> -}
> -
>  static void arc_pgu_crtc_atomic_begin(struct drm_crtc *crtc,
>  				      struct drm_crtc_state *state)
>  {
> @@ -158,6 +167,7 @@ static void arc_pgu_crtc_atomic_begin(struct drm_crtc
> *crtc, }
> 
>  static const struct drm_crtc_helper_funcs arc_pgu_crtc_helper_funcs = {
> +	.mode_valid	= arc_pgu_crtc_mode_valid,
>  	.mode_set	= drm_helper_crtc_mode_set,
>  	.mode_set_base	= drm_helper_crtc_mode_set_base,
>  	.mode_set_nofb	= arc_pgu_crtc_mode_set_nofb,
> @@ -165,7 +175,6 @@ static void arc_pgu_crtc_atomic_begin(struct drm_crtc
> *crtc, .disable	= arc_pgu_crtc_disable,
>  	.prepare	= arc_pgu_crtc_disable,
>  	.commit		= arc_pgu_crtc_enable,
> -	.atomic_check	= arc_pgu_crtc_atomic_check,
>  	.atomic_begin	= arc_pgu_crtc_atomic_begin,
>  };

-- 
Regards,

Laurent Pinchart