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

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Message-ID: <1820767.5KxKD5qtyk@diego>
Date: Wed, 11 Dec 2024 18:23:03 +0100
From: Heiko Stübner <heiko@...ech.de>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>,
 Maxime Ripard <mripard@...nel.org>
Cc: Sandy Huang <hjc@...k-chips.com>, Andy Yan <andy.yan@...k-chips.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
 kernel@...labora.com, dri-devel@...ts.freedesktop.org,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
 FUKAUMI Naoki <naoki@...xa.com>
Subject:
 Re: [PATCH v2 3/5] drm/rockchip: vop2: Improve display modes handling on
 RK3588 HDMI0

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@...z, 2048x1152@...z, 1024x768@...z 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@...z.
> > 
> > Tested-by: FUKAUMI Naoki <naoki@...xa.com>
> > Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.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@...z, 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.