Subject: [PATCH 7/8] drm: atmel-hlcdc: add and configure LVDS PLL clock support

From: Manikandan Muralidharan <[email-masked]>
Date: Tue, 19 May 2026 14:31:34 +0530

Set the LVDS PLL rate to 7x the pixel clock.
set ATMEL_XLCDC_CLKBYP for the LVDS path, leaving clock
lifecycle management to the atomic callbacks and fallback to
sys_clk for non-LVDS displays with proper error handling.

Signed-off-by: Manikandan Muralidharan <[email-masked]>
---
 .../gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c    | 45 +++++++++++++++++--
 1 file changed, 42 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
index f837684654ea..73a8650bc9b7 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
@@ -26,6 +26,8 @@
 
 #include "atmel_hlcdc_dc.h"
 
+#define ATMEL_LVDS_PLL_MULT	7
+
 /**
  * struct atmel_hlcdc_crtc_state - Atmel HLCDC CRTC state structure
  *
@@ -66,6 +68,14 @@ drm_crtc_to_atmel_hlcdc_crtc(struct drm_crtc *crtc)
 	return container_of(crtc, struct atmel_hlcdc_crtc, base);
 }
 
+static void atmel_hlcdc_crtc_disable_clock(struct atmel_hlcdc_crtc *crtc)
+{
+	if (crtc->dc->hlcdc->lvds_pll_clk)
+		clk_disable_unprepare(crtc->dc->hlcdc->lvds_pll_clk);
+	else
+		clk_disable_unprepare(crtc->dc->hlcdc->sys_clk);
+}
+
 static int atmel_hlcdc_crtc_setup_clock(struct atmel_hlcdc_crtc *crtc,
 					unsigned long mode_rate,
 					unsigned int *cfg,
@@ -74,6 +84,12 @@ static int atmel_hlcdc_crtc_setup_clock(struct atmel_hlcdc_crtc *crtc,
 	unsigned long prate;
 	int div, ret;
 
+	if (crtc->dc->hlcdc->lvds_pll_clk) {
+		*cfg |= ATMEL_XLCDC_CLKBYP;
+		*mask |= ATMEL_XLCDC_CLKBYP;
+		return clk_prepare_enable(crtc->dc->hlcdc->lvds_pll_clk);
+	}
+
 	ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
 	if (ret)
 		return ret;
@@ -198,7 +214,7 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
 			   ATMEL_XLCDC_DPI : ATMEL_HLCDC_MODE_MASK),
 			   cfg);
 
-	clk_disable_unprepare(crtc->dc->hlcdc->sys_clk);
+	atmel_hlcdc_crtc_disable_clock(crtc);
 }
 
 static enum drm_mode_status
@@ -254,7 +270,8 @@ static void atmel_hlcdc_crtc_atomic_disable(struct drm_crtc *c,
 				    10, 1000))
 		drm_warn(dev, "Atmel LCDC status register CLKSTS timeout\n");
 
-	clk_disable_unprepare(crtc->dc->hlcdc->sys_clk);
+	atmel_hlcdc_crtc_disable_clock(crtc);
+
 	pinctrl_pm_select_sleep_state(dev->dev);
 
 	pm_runtime_allow(dev->dev);
@@ -267,15 +284,33 @@ static void atmel_hlcdc_crtc_atomic_enable(struct drm_crtc *c,
 {
 	struct drm_device *dev = c->dev;
 	struct atmel_hlcdc_crtc *crtc = drm_crtc_to_atmel_hlcdc_crtc(c);
+	struct drm_display_mode *adj = &c->state->adjusted_mode;
 	struct regmap *regmap = crtc->dc->hlcdc->regmap;
 	unsigned int status;
+	int ret;
 
 	pm_runtime_get_sync(dev->dev);
 
 	pm_runtime_forbid(dev->dev);
 
 	pinctrl_pm_select_default_state(dev->dev);
-	clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
+
+	/*
+	 * Set LVDS PLL clock rate (7x pixel clock) if available
+	 */
+	if (crtc->dc->hlcdc->lvds_pll_clk) {
+		ret = clk_set_rate(crtc->dc->hlcdc->lvds_pll_clk,
+				   adj->clock * 1000 * ATMEL_LVDS_PLL_MULT);
+		if (ret) {
+			drm_err(dev, "Failed to set LVDS PLL clk rate: %d\n", ret);
+			goto err_clk;
+		}
+		ret = clk_prepare_enable(crtc->dc->hlcdc->lvds_pll_clk);
+	} else {
+		ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
+	}
+	if (ret)
+		goto err_clk;
 
 	regmap_write(regmap, ATMEL_HLCDC_EN, ATMEL_HLCDC_PIXEL_CLK);
 	if (regmap_read_poll_timeout(regmap, ATMEL_HLCDC_SR, status,
@@ -310,7 +345,11 @@ static void atmel_hlcdc_crtc_atomic_enable(struct drm_crtc *c,
 	}
 
 	pm_runtime_put_sync(dev->dev);
+	return;
 
+err_clk:
+	pm_runtime_allow(dev->dev);
+	pm_runtime_put_sync(dev->dev);
 }
 
 #define ATMEL_HLCDC_RGB444_OUTPUT		BIT(0)
-- 
2.25.1