linux-kernel - Re: [PATCH v6 08/13] drm/sun4i: add support for Allwinner DE2 mixers

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Date:   Fri, 05 May 2017 20:39:31 +0800
From:   Icenowy Zheng <icenowy@...c.io>
To:     linux-arm-kernel@...ts.infradead.org,
        Maxime Ripard <maxime.ripard@...e-electrons.com>
CC:     devicetree@...r.kernel.org, linux-sunxi@...glegroups.com,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v6 08/13] drm/sun4i: add support for Allwinner DE2 mixers



于 2017年5月5日 GMT+08:00 下午8:36:18, Maxime Ripard <maxime.ripard@...e-electrons.com> 写到:
>On Fri, May 05, 2017 at 12:50:51AM +0800, icenowy@...c.io wrote:
>> > > +void sun8i_mixer_layer_enable(struct sun8i_mixer *mixer,
>> > > +				int layer, bool enable)
>> > > +{
>> > > +	u32 val;
>> > > +	/* Currently the first UI channel is used */
>> > > +	int chan = mixer->cfg->vi_num;
>> > > +
>> > > +	DRM_DEBUG_DRIVER("Enabling layer %d in channel %d\n", layer,
>chan);
>> > > +
>> > > +	if (enable)
>> > > +		val = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_EN;
>> > > +	else
>> > > +		val = 0;
>> > > +
>> > > +	regmap_update_bits(mixer->engine.regs,
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR(chan, layer),
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR_EN, val);
>> > > +
>> > > +	/* Set the alpha configuration */
>> > > +	regmap_update_bits(mixer->engine.regs,
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR(chan, layer),
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_MASK,
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_DEF);
>> > > +	regmap_update_bits(mixer->engine.regs,
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR(chan, layer),
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MASK,
>> > > +			   SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_DEF);
>> > > +}
>> > 
>> > This one too.
>> 
>> It's called from sun8i_layer.c, so it cannot be static.
>
>Fair enough.
>
>> > > +	/* Set base coordinates */
>> > > +	DRM_DEBUG_DRIVER("Layer coordinates X: %d Y: %d\n",
>> > > +			 state->crtc_x, state->crtc_y);
>> > > +	regmap_write(mixer->engine.regs,
>> > > +		     SUN8I_MIXER_CHAN_UI_LAYER_COORD(chan, layer),
>> > > +		     SUN8I_MIXER_COORD(state->crtc_x, state->crtc_y));
>> > 
>> > X and Y are fixed point numbers. You want to keep only the higher
>16
>> > bits there.
>> 
>> Do you mean "lower 16 bits"? Thus should I (x & 0xffff) or ((u16)x) ?
>
>Nevermind, I got confused with src_x and src_y.
>
>> P.S. The negative coordinates are broken, how should I deal with it?
>or
>> is the coordinates promised to be not negative?
>
>Adjust the buffer base address, and use a shorter line. You have such
>an example in the sun4i code.

Are they these two lines:
```
paddr += (state->src_x >> 16) * bpp;
paddr += (state->src_y >> 16) * fb->pitches[0];
```

I think I copied them here, so I don't need to mind this problem any more, right?

>
>Maxime