linux-kernel - [PATCH v2 3/3] drm: atmel-hlcdc: set LVDS PLL clock rate for LVDS Displays

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Message-ID: <20250212094449.109622-3-manikandan.m@microchip.com>
Date: Wed, 12 Feb 2025 15:14:49 +0530
From: Manikandan Muralidharan <manikandan.m@...rochip.com>
To: <sam@...nborg.org>, <bbrezillon@...nel.org>,
	<maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
	<tzimmermann@...e.de>, <airlied@...il.com>, <simona@...ll.ch>,
	<nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
	<claudiu.beznea@...on.dev>, <lee@...nel.org>,
	<dri-devel@...ts.freedesktop.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>
CC: Dharma Balasubiramani <dharma.b@...rochip.com>, Manikandan Muralidharan
	<manikandan.m@...rochip.com>
Subject: [PATCH v2 3/3] drm: atmel-hlcdc: set LVDS PLL clock rate for LVDS Displays

From: Dharma Balasubiramani <dharma.b@...rochip.com>

The LVDS PLL clock runs at 7 times the panel pixel clock.
For LVDS displays, the PLL clock rate is set based on the
panel pixel clock, eliminating the need for the assigned-clock-rates
Device Tree property for lvds_pll_clk in the LCD node.

Signed-off-by: Dharma Balasubiramani <dharma.b@...rochip.com>
Signed-off-by: Manikandan Muralidharan <manikandan.m@...rochip.com>
---
Changes in v2:
- Rephrase commit message and comment block
---
 .../gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c    | 48 ++++++++++++++++---
 1 file changed, 42 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
index 0e709047369a..cf4f9ccd81a4 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
@@ -99,9 +99,15 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
 		drm_connector_list_iter_end(&iter);
 	}
 
-	ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
-	if (ret)
-		return;
+	if (crtc->dc->hlcdc->lvds_pll_clk) {
+		ret = clk_prepare_enable(crtc->dc->hlcdc->lvds_pll_clk);
+		if (ret)
+			return;
+	} else {
+		ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
+		if (ret)
+			return;
+	}
 
 	vm.vfront_porch = adj->crtc_vsync_start - adj->crtc_vdisplay;
 	vm.vback_porch = adj->crtc_vtotal - adj->crtc_vsync_end;
@@ -186,7 +192,10 @@ 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);
+	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 enum drm_mode_status
@@ -242,7 +251,11 @@ static void atmel_hlcdc_crtc_atomic_disable(struct drm_crtc *c,
 				    10, 1000))
 		dev_warn(dev->dev, "Atmel LCDC status register CLKSTS timeout\n");
 
-	clk_disable_unprepare(crtc->dc->hlcdc->sys_clk);
+	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);
+
 	pinctrl_pm_select_sleep_state(dev->dev);
 
 	pm_runtime_allow(dev->dev);
@@ -255,15 +268,38 @@ 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);
+
+	if (crtc->dc->hlcdc->lvds_pll_clk) {
+		/*
+		 * For LVDS displays, retrieve the pixel clock from the panel
+		 * and set the LVDS PLL clock rate accordingly.
+		 * According to the datasheet,the LVDS PLL clock is 7 times the pixel clock.
+		 */
+		ret = clk_set_rate(crtc->dc->hlcdc->lvds_pll_clk,
+				   (adj->clock * 7 * 1000));
+		if (ret) {
+			dev_err(dev->dev, "Failed to set LVDS PLL clk rate: %d\n", ret);
+			return;
+		}
+
+		ret = clk_prepare_enable(crtc->dc->hlcdc->lvds_pll_clk);
+		if (ret)
+			return;
+	} else {
+		ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
+		if (ret)
+			return;
+	}
 
 	regmap_write(regmap, ATMEL_HLCDC_EN, ATMEL_HLCDC_PIXEL_CLK);
 	if (regmap_read_poll_timeout(regmap, ATMEL_HLCDC_SR, status,
-- 
2.25.1