linux-kernel - [PATCH v3 1/5] drm/rockchip: vop2: Check bpc before switching DCLK source

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Message-Id: <20251021-rk3588-10bpc-v3-1-3d3eed00a6db@collabora.com>
Date: Tue, 21 Oct 2025 13:19:14 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Sandy Huang <hjc@...k-chips.com>, 
 Heiko Stübner <heiko@...ech.de>, 
 Andy Yan <andy.yan@...k-chips.com>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, Daniel Stone <daniels@...labora.com>
Subject: [PATCH v3 1/5] drm/rockchip: vop2: Check bpc before switching DCLK
 source

When making use of the HDMI PHY PLL as a VOP2 DCLK source, it's output
rate does normally match the mode clock.  But this is only applicable
for default color depth of 8 bpc.  For higher depths, the output clock
is further divided by the hardware according to the formula:

  output rate = PHY PLL rate * 8 / bpc

Hence there is no need for VOP2 to compensate for bpc when adjusting
DCLK, but it is required to do so when computing its maximum operating
frequency.

Take color depth into consideration before deciding to switch DCLK
source.

Reviewed-by: Daniel Stone <daniels@...labora.com>
Acked-by: Daniel Stone <daniels@...labora.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 58 +++++++++++++++-------------
 1 file changed, 32 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index 284c8a048034..54176298a53b 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
@@ -101,7 +101,7 @@ enum vop2_afbc_format {
 	VOP2_AFBC_FMT_INVALID = -1,
 };
 
-#define VOP2_MAX_DCLK_RATE		600000000
+#define VOP2_MAX_DCLK_RATE		600000000UL
 
 /*
  * bus-format types.
@@ -1742,36 +1742,42 @@ static void vop2_crtc_atomic_enable(struct drm_crtc *crtc,
 	 * 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 || vop2->pll_hdmiphy1) && 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 (!vop2->pll_hdmiphy0)
+	if (vop2->pll_hdmiphy0 || vop2->pll_hdmiphy1) {
+		unsigned long max_dclk = DIV_ROUND_CLOSEST_ULL(VOP2_MAX_DCLK_RATE * 8,
+							       vcstate->output_bpc);
+		if (clock <= max_dclk) {
+			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 (!vop2->pll_hdmiphy0)
+						break;
+
+					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;
+				}
 
-				if (!vp->dclk_src)
-					vp->dclk_src = clk_get_parent(vp->dclk);
+				if (rkencoder->crtc_endpoint_id == ROCKCHIP_VOP2_EP_HDMI1) {
+					if (!vop2->pll_hdmiphy1)
+						break;
 
-				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;
-			}
+					if (!vp->dclk_src)
+						vp->dclk_src = clk_get_parent(vp->dclk);
 
-			if (rkencoder->crtc_endpoint_id == ROCKCHIP_VOP2_EP_HDMI1) {
-				if (!vop2->pll_hdmiphy1)
+					ret = clk_set_parent(vp->dclk, vop2->pll_hdmiphy1);
+					if (ret < 0)
+						drm_warn(vop2->drm,
+							 "Could not switch to HDMI1 PHY PLL: %d\n",
+							 ret);
 					break;
-
-				if (!vp->dclk_src)
-					vp->dclk_src = clk_get_parent(vp->dclk);
-
-				ret = clk_set_parent(vp->dclk, vop2->pll_hdmiphy1);
-				if (ret < 0)
-					drm_warn(vop2->drm,
-						 "Could not switch to HDMI1 PHY PLL: %d\n", ret);
-				break;
+				}
 			}
 		}
 	}

-- 
2.51.0