[PATCH] drm: atmel-hlcdc: Support inverting the pixel clock polarity

* [PATCH] drm: atmel-hlcdc: Support inverting the pixel clock polarity
@ 2023-06-09 14:48 Miquel Raynal
       [not found] ` <20230610200515.GA1041001@ravnborg.org>
  0 siblings, 1 reply; 8+ messages in thread
From: Miquel Raynal @ 2023-06-09 14:48 UTC (permalink / raw)
  To: Sam Ravnborg, Boris Brezillon, David Airlie, Daniel Vetter,
	dri-devel
  Cc: Alexandre Belloni, Thomas Petazzoni, Miquel Raynal,
	Claudiu Beznea, linux-arm-kernel

On the SoC host controller, the pixel clock can be:
* standard: data is launched on the rising edge
* inverted: data is launched on the falling edge

Some panels may need the inverted option to be used so let's support
this DRM flag.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---

Hello, this change was tested on a Sama5d36 based custom board with a
panel not behaving correctly if the pixel clock was not inverted.
Cheers, Miquèl

 .../gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c    | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
index 58184cd6ab0b..cc5cf4c2faf7 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
@@ -68,7 +68,11 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
 	struct atmel_hlcdc_crtc *crtc = drm_crtc_to_atmel_hlcdc_crtc(c);
 	struct regmap *regmap = crtc->dc->hlcdc->regmap;
 	struct drm_display_mode *adj = &c->state->adjusted_mode;
+	struct drm_encoder *encoder = NULL, *en_iter;
+	struct drm_connector *connector = NULL;
 	struct atmel_hlcdc_crtc_state *state;
+	struct drm_device *ddev = c->dev;
+	struct drm_connector_list_iter iter;
 	unsigned long mode_rate;
 	struct videomode vm;
 	unsigned long prate;
@@ -76,6 +80,23 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
 	unsigned int cfg = 0;
 	int div, ret;
 
+	/* get encoder from crtc */
+	drm_for_each_encoder(en_iter, ddev) {
+		if (en_iter->crtc == c) {
+			encoder = en_iter;
+			break;
+		}
+	}
+
+	if (encoder) {
+		/* Get the connector from encoder */
+		drm_connector_list_iter_begin(ddev, &iter);
+		drm_for_each_connector_iter(connector, &iter)
+			if (connector->encoder == encoder)
+				break;
+		drm_connector_list_iter_end(&iter);
+	}
+
 	ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
 	if (ret)
 		return;
@@ -134,6 +155,10 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
 
 	cfg |= ATMEL_HLCDC_CLKDIV(div);
 
+	if (connector &&
+	    connector->display_info.bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
+		cfg |= ATMEL_HLCDC_CLKPOL;
+
 	regmap_update_bits(regmap, ATMEL_HLCDC_CFG(0), mask, cfg);
 
 	state = drm_crtc_state_to_atmel_hlcdc_crtc_state(c->state);
-- 
2.34.1


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