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

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Date:   Mon, 2 Mar 2020 18:01:21 +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,
 
On Mon, Mar 02, 2020 at 04:54:17PM +0100, Neil Armstrong wrote:
> On 02/03/2020 10:05, Laurent Pinchart wrote:
> > 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) &&
> > 
> 
> I fixed the calculus and the cast, but I'll rename the mtmdsclock in a following patch.
> 
> is it ok for you ?

Sure, works for me.

-- 
Regards,

Laurent Pinchart