Re: [PATCH v2 3/5] drm/rockchip: vop2: Improve display modes handling on RK3588 HDMI0

["Heiko Stübner" <heiko@sntech.de>]

Am Mittwoch, 11. Dezember 2024, 18:47:44 CET schrieb Maxime Ripard:
> On Wed, Dec 11, 2024 at 06:23:03PM +0100, Heiko Stübner wrote:
> > Am Mittwoch, 11. Dezember 2024, 18:07:57 CET schrieb Maxime Ripard:
> > > On Wed, Dec 11, 2024 at 12:15:07PM +0200, Cristian Ciocaltea wrote:
> > > > The RK3588 specific implementation is currently quite limited in terms
> > > > of handling the full range of display modes supported by the connected
> > > > screens, e.g. 2560x1440@75Hz, 2048x1152@60Hz, 1024x768@60Hz are just a
> > > > few of them.
> > > > 
> > > > Additionally, it doesn't cope well with non-integer refresh rates like
> > > > 59.94, 29.97, 23.98, etc.
> > > > 
> > > > Make use of HDMI0 PHY PLL as a more accurate DCLK source to handle
> > > > all display modes up to 4K@60Hz.
> > > > 
> > > > Tested-by: FUKAUMI Naoki <naoki@radxa.com>
> > > > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
> > > > ---
> > > >  drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 34 ++++++++++++++++++++++++++++
> > > >  1 file changed, 34 insertions(+)
> > > > 
> > > > diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> > > > index 8b2f53ffefdbf1cc8737b3a86e630a03a7fd9348..393fe6aa170aaee9663c4a6d98c1cd6a5ef79392 100644
> > > > --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> > > > +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
> > > > @@ -158,6 +158,7 @@ struct vop2_video_port {
> > > >  	struct drm_crtc crtc;
> > > >  	struct vop2 *vop2;
> > > >  	struct clk *dclk;
> > > > +	struct clk *dclk_src;
> > > >  	unsigned int id;
> > > >  	const struct vop2_video_port_data *data;
> > > >  
> > > > @@ -212,6 +213,7 @@ struct vop2 {
> > > >  	struct clk *hclk;
> > > >  	struct clk *aclk;
> > > >  	struct clk *pclk;
> > > > +	struct clk *pll_hdmiphy0;
> > > >  
> > > >  	/* optional internal rgb encoder */
> > > >  	struct rockchip_rgb *rgb;
> > > > @@ -220,6 +222,8 @@ struct vop2 {
> > > >  	struct vop2_win win[];
> > > >  };
> > > >  
> > > > +#define VOP2_MAX_DCLK_RATE		600000 /* kHz */
> > > > +
> > > >  #define vop2_output_if_is_hdmi(x)	((x) == ROCKCHIP_VOP2_EP_HDMI0 || \
> > > >  					 (x) == ROCKCHIP_VOP2_EP_HDMI1)
> > > >  
> > > > @@ -1033,6 +1037,9 @@ static void vop2_crtc_atomic_disable(struct drm_crtc *crtc,
> > > >  
> > > >  	vop2_crtc_disable_irq(vp, VP_INT_DSP_HOLD_VALID);
> > > >  
> > > > +	if (vp->dclk_src)
> > > > +		clk_set_parent(vp->dclk, vp->dclk_src);
> > > > +
> > > >  	clk_disable_unprepare(vp->dclk);
> > > >  
> > > >  	vop2->enable_count--;
> > > > @@ -2049,6 +2056,27 @@ static void vop2_crtc_atomic_enable(struct drm_crtc *crtc,
> > > >  
> > > >  	vop2_vp_write(vp, RK3568_VP_MIPI_CTRL, 0);
> > > >  
> > > > +	/*
> > > > +	 * Switch to HDMI PHY PLL as DCLK source for display modes up
> > > > +	 * to 4K@60Hz, if available, otherwise keep using the system CRU.
> > > > +	 */
> > > > +	if (vop2->pll_hdmiphy0 && mode->crtc_clock <= VOP2_MAX_DCLK_RATE) {
> > > > +		drm_for_each_encoder_mask(encoder, crtc->dev, crtc_state->encoder_mask) {
> > > > +			struct rockchip_encoder *rkencoder = to_rockchip_encoder(encoder);
> > > > +
> > > > +			if (rkencoder->crtc_endpoint_id == ROCKCHIP_VOP2_EP_HDMI0) {
> > > > +				if (!vp->dclk_src)
> > > > +					vp->dclk_src = clk_get_parent(vp->dclk);
> > > > +
> > > > +				ret = clk_set_parent(vp->dclk, vop2->pll_hdmiphy0);
> > > > +				if (ret < 0)
> > > > +					drm_warn(vop2->drm,
> > > > +						 "Could not switch to HDMI0 PHY PLL: %d\n", ret);
> > > > +				break;
> > > > +			}
> > > > +		}
> > > > +	}
> > > > +
> > > 
> > > It seems pretty fragile to do it at atomic_enable time, even more so
> > > since you don't lock the parent either.
> > > 
> > > Any reason not to do it in the DRM or clock driver probe, and make sure
> > > you never change the parent somehow?
> > 
> > On rk3588 we have 3 dclk_s and 2 hdmi controllers. Each video-port can
> > use the clock generated from either the hdmi0phy or hdmi1phy, depending
> > on which hdmi-controller it uses.
> > 
> > So you actually need to know which vpX will output to which hdmiY to then
> > reparent that dclk to the hdmiphy output.
> 
> The Rockchip nomenclature isn't super obvious to me, sorry. Is there a
> datasheet for this somewhere? Also, does this vpX -> HDMI-Y mapping need
> to be dynamic?

VPs are CRTCs in drm-language and each of them can drive a differing
number of output encoders. Those video-ports also have differing output
characteristics in terms of supported resolution and other properties.

The rk3588 TRM has leaked in a number of places, and if you find a
TRM-part2, there is a section labeled "Display Output Interface Description"
that has a nice graphic for that.

Or in short:
- CRTC(VP)0 supports 8K resolution and can drive DP0+1, HDMI0+1, eDP0+1
  [if I'm reading things correctly, 8K together with CRTC1 somehow)
- CRTC(VP)1 supports 4K resolution and can drive DP0+1, HDMI0+1, eDP0+1
- CRTC(VP)2 supports 4K resolution and can drive DP0+1, HDMI0+1, eDP01, DSI0+1
- CRTC(VP)3 supports 2K resolution and can drive DSI0+1 and some BT1120,BT656

so for the 3 higher resolution CRTCs there are essentially 6 or 8 output options
depending on the board design