linux-kernel - Re: [PATCH v4 01/11] drm/bridge: dw-hdmi: set mtmdsclock for deep color

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Message-ID: <20200302090527.GB11960@pendragon.ideasonboard.com>
Date:   Mon, 2 Mar 2020 11:05:27 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     a.hajda@...sung.com, jonas@...boo.se, jernej.skrabec@...l.net,
        boris.brezillon@...labora.com, linux-amlogic@...ts.infradead.org,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 01/11] drm/bridge: dw-hdmi: set mtmdsclock for deep
 color

Hi Neil and Jonas,

Thank you for the patch.

On Thu, Feb 06, 2020 at 08:18:24PM +0100, Neil Armstrong wrote:
> From: Jonas Karlman <jonas@...boo.se>
> 
> Configure the correct mtmdsclock for deep colors to prepare support
> for 10, 12 & 16bit output.
> 
> Signed-off-by: Jonas Karlman <jonas@...boo.se>
> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 67fca439bbfb..9e0927d22db6 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -1818,9 +1818,26 @@ static void hdmi_av_composer(struct dw_hdmi *hdmi,
>  
>  	dev_dbg(hdmi->dev, "final pixclk = %d\n", vmode->mpixelclock);

Nitpicking a bit, I would change

-	vmode->mtmdsclock = vmode->mpixelclock = mode->clock * 1000;
+	vmode->mpixelclock = mode->clock * 1000;

above, and here add

	vmode->mtmdsclock = vmode->mpixelclock;

to keep all mtmdsclock calculation in a single place.

> +	if (!hdmi_bus_fmt_is_yuv422(hdmi->hdmi_data.enc_out_bus_format)) {
> +		switch (hdmi_bus_fmt_color_depth(
> +				hdmi->hdmi_data.enc_out_bus_format)) {
> +		case 16:
> +			vmode->mtmdsclock = (u64)vmode->mpixelclock * 2;

Both mpixelclock and mtmdsclock are unsigned int. Is the cast to u64
needed ?

On a separate but related note, what does the 'm' in tmdsclock stand for
? It seems to originate from the 'm' prefix for mpixelclock, which has
been there from the start. Unless there's a good reason for the prefix,
renaming mtmdsclock to tmds_clock (and handling the other fields in the
hdmi_vmode structure similarly) would increase clarity I think.

> +			break;
> +		case 12:
> +			vmode->mtmdsclock = (u64)vmode->mpixelclock * 3 / 2;
> +			break;
> +		case 10:
> +			vmode->mtmdsclock = (u64)vmode->mpixelclock * 5 / 4;
> +			break;
> +		}
> +	}
> +
>  	if (hdmi_bus_fmt_is_yuv420(hdmi->hdmi_data.enc_out_bus_format))
>  		vmode->mtmdsclock /= 2;
>  
> +	dev_dbg(hdmi->dev, "final tmdsclk = %d\n", vmode->mtmdsclock);

s/tmdsclk/tmdsclock/ to match the field name ?

> +
>  	/* Set up HDMI_FC_INVIDCONF */
>  	inv_val = (hdmi->hdmi_data.hdcp_enable ||
>  		   (dw_hdmi_support_scdc(hdmi) &&

-- 
Regards,

Laurent Pinchart