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From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Ulrich Hecht <uli@fpond.eu>
Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
        dri-devel@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org,
        Kieran Bingham <kieran.bingham@ideasonboard.com>
Subject: Re: [PATCH v2 04/16] drm: bridge: thc63: Restrict modes based on hardware operating frequency
Date: Mon, 17 Sep 2018 15:23:28 +0300
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Hi Ulrich,

On Monday, 17 September 2018 13:53:43 EEST Ulrich Hecht wrote:
> > On September 14, 2018 at 11:10 AM Laurent Pinchart wrote:
> > 
> > The THC63LVD1024 is restricted to a pixel clock frequency in the range
> > of 8 to 135 MHz. Implement the bridge .mode_valid() operation
> > accordingly.
> > 
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
> > Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
> > Tested-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
> > ---
> > 
> >  drivers/gpu/drm/bridge/thc63lvd1024.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/bridge/thc63lvd1024.c
> > b/drivers/gpu/drm/bridge/thc63lvd1024.c index c8b9edd5a7f4..63609ba16b6d
> > 100644
> > --- a/drivers/gpu/drm/bridge/thc63lvd1024.c
> > +++ b/drivers/gpu/drm/bridge/thc63lvd1024.c
> > @@ -45,6 +45,23 @@ static int thc63_attach(struct drm_bridge *bridge)
> >  	return drm_bridge_attach(bridge->encoder, thc63->next, bridge);
> >  }
> > 
> > +static enum drm_mode_status thc63_mode_valid(struct drm_bridge *bridge,
> > +					const struct drm_display_mode *mode)
> > +{
> > +	/*
> > +	 * The THC63LVD0124 clock frequency range is 8 to 135 MHz in single-in,
> 
> That should be THC63LVD1024.

Will be fixed in v3.

> > +	 * single-out mode.
> 
> For the input clock (that's what we're talking about, right?), that also
> applies to single-in/dual-out. Maybe just omit the "single-out" clause?

Good point, I'll change that in v3.

> > Note that the limits depends on the mode and will
> > +	 * need to be adjusted accordingly.
> > +	 */
> 
> I don't quite understand. Does that refer to the THC63 mode, or the DRM
> mode?

This refers to the THC63 mode, I'll clarify this in v3 as well.

> > +	if (mode->clock < 8000)
> > +		return MODE_CLOCK_LOW;
> > +
> > +	if (mode->clock > 135000)
> > +		return MODE_CLOCK_HIGH;
> > +
> > +	return MODE_OK;
> > +}
> > +
> >  static void thc63_enable(struct drm_bridge *bridge)
> >  {
> >  	struct thc63_dev *thc63 = to_thc63(bridge);
> > @@ -77,6 +94,7 @@ static void thc63_disable(struct drm_bridge *bridge)
> > 
> >  static const struct drm_bridge_funcs thc63_bridge_func = {
> >  	.attach	= thc63_attach,
> > +	.mode_valid = thc63_mode_valid,
> >  	.enable = thc63_enable,
> >  	.disable = thc63_disable,
> >  };

-- 
Regards,

Laurent Pinchart