[PATCH v4 04/25] drm/tilcdc: Add support for DRM bus flags and simplify panel config

["Kory Maincent (TI.com)" <kory.maincent@bootlin.com>]

Migrate CRTC mode configuration to use standard DRM bus flags in
preparation for removing the tilcdc_panel driver and its custom
tilcdc_panel_info structure.

Add support for DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE and
DRM_BUS_FLAG_SYNC_DRIVE_NEGEDGE flags to control pixel clock and sync
signal edge polarity, while maintaining backward compatibility with the
existing tilcdc panel info structure.

Simplify several hardware parameters by setting them to fixed defaults
based on common usage across existing device trees:
- DMA burst size: 16 (previously configurable via switch statement)
- AC bias frequency: 255 (previously panel-specific)
- FIFO DMA request delay: 128 (previously panel-specific)

These parameters show no variation in real-world usage, so hardcoding
them simplifies the driver without losing functionality.

Preserve FIFO threshold configurability by detecting the SoC type, as
this parameter varies between AM33xx (8) and DA850 (16) platforms.

Signed-off-by: Kory Maincent (TI.com) <kory.maincent@bootlin.com>
---
Change in v4:
- Use of_device_get_match_data() instead of of_match_node().
- Move back the tilcdc_of_match table down were it was before.

Change in v2:
- Use SoC type instead of devicetree parameter to set FIFO threshold
  value.
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 47 +++++++++++++-----------------------
 drivers/gpu/drm/tilcdc/tilcdc_drv.c  | 17 +++++++++++--
 drivers/gpu/drm/tilcdc/tilcdc_drv.h  |  2 ++
 3 files changed, 34 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index b06b1453db2dd..2309a9a0c925d 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -285,27 +285,15 @@ static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
 
 	/* Configure the Burst Size and fifo threshold of DMA: */
 	reg = tilcdc_read(dev, LCDC_DMA_CTRL_REG) & ~0x00000770;
-	switch (info->dma_burst_sz) {
-	case 1:
-		reg |= LCDC_DMA_BURST_SIZE(LCDC_DMA_BURST_1);
-		break;
-	case 2:
-		reg |= LCDC_DMA_BURST_SIZE(LCDC_DMA_BURST_2);
-		break;
-	case 4:
-		reg |= LCDC_DMA_BURST_SIZE(LCDC_DMA_BURST_4);
-		break;
-	case 8:
-		reg |= LCDC_DMA_BURST_SIZE(LCDC_DMA_BURST_8);
-		break;
-	case 16:
-		reg |= LCDC_DMA_BURST_SIZE(LCDC_DMA_BURST_16);
-		break;
-	default:
-		dev_err(dev->dev, "invalid burst size\n");
-		return;
+	/* Use 16 bit DMA burst size by default */
+	reg |= LCDC_DMA_BURST_SIZE(LCDC_DMA_BURST_16);
+	if (priv->fifo_th) {
+		int fifo_th_val = ilog2(priv->fifo_th) - 3;
+
+		reg |= (fifo_th_val << 8);
+	} else {
+		reg |= (info->fifo_th << 8);
 	}
-	reg |= (info->fifo_th << 8);
 	tilcdc_write(dev, LCDC_DMA_CTRL_REG, reg);
 
 	/* Configure timings: */
@@ -321,8 +309,8 @@ static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
 
 	/* Set AC Bias Period and Number of Transitions per Interrupt: */
 	reg = tilcdc_read(dev, LCDC_RASTER_TIMING_2_REG) & ~0x000fff00;
-	reg |= LCDC_AC_BIAS_FREQUENCY(info->ac_bias) |
-		LCDC_AC_BIAS_TRANSITIONS_PER_INT(info->ac_bias_intrpt);
+	/* Use 255 AC Bias Pin Frequency by default */
+	reg |= LCDC_AC_BIAS_FREQUENCY(255);
 
 	/*
 	 * subtract one from hfp, hbp, hsw because the hardware uses
@@ -392,20 +380,19 @@ static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
 			return;
 		}
 	}
-	reg |= info->fdd << 12;
+	/* Use 128 FIFO DMA Request Delay by default */
+	reg |= 128 << 12;
 	tilcdc_write(dev, LCDC_RASTER_CTRL_REG, reg);
 
-	if (info->invert_pxl_clk)
+	if (info->invert_pxl_clk ||
+	    mode->flags == DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
 		tilcdc_set(dev, LCDC_RASTER_TIMING_2_REG, LCDC_INVERT_PIXEL_CLOCK);
 	else
 		tilcdc_clear(dev, LCDC_RASTER_TIMING_2_REG, LCDC_INVERT_PIXEL_CLOCK);
 
-	if (info->sync_ctrl)
-		tilcdc_set(dev, LCDC_RASTER_TIMING_2_REG, LCDC_SYNC_CTRL);
-	else
-		tilcdc_clear(dev, LCDC_RASTER_TIMING_2_REG, LCDC_SYNC_CTRL);
-
-	if (info->sync_edge)
+	tilcdc_set(dev, LCDC_RASTER_TIMING_2_REG, LCDC_SYNC_CTRL);
+	if (info->sync_edge ||
+	    mode->flags == DRM_BUS_FLAG_SYNC_DRIVE_NEGEDGE)
 		tilcdc_set(dev, LCDC_RASTER_TIMING_2_REG, LCDC_SYNC_EDGE);
 	else
 		tilcdc_clear(dev, LCDC_RASTER_TIMING_2_REG, LCDC_SYNC_EDGE);
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_drv.c b/drivers/gpu/drm/tilcdc/tilcdc_drv.c
index 3dcbec312bacb..fe01f3fcaf3c2 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_drv.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.c
@@ -31,6 +31,11 @@
 #include "tilcdc_panel.h"
 #include "tilcdc_regs.h"
 
+enum tilcdc_variant {
+	AM33XX_TILCDC,
+	DA850_TILCDC,
+};
+
 static LIST_HEAD(module_list);
 
 static const u32 tilcdc_rev1_formats[] = { DRM_FORMAT_RGB565 };
@@ -198,6 +203,7 @@ static int tilcdc_init(const struct drm_driver *ddrv, struct device *dev)
 	struct platform_device *pdev = to_platform_device(dev);
 	struct device_node *node = dev->of_node;
 	struct tilcdc_drm_private *priv;
+	enum tilcdc_variant variant;
 	u32 bpp = 0;
 	int ret;
 
@@ -209,6 +215,8 @@ static int tilcdc_init(const struct drm_driver *ddrv, struct device *dev)
 	if (IS_ERR(ddev))
 		return PTR_ERR(ddev);
 
+	variant = (uintptr_t)of_device_get_match_data(dev);
+
 	ddev->dev_private = priv;
 	platform_set_drvdata(pdev, ddev);
 	drm_mode_config_init(ddev);
@@ -309,6 +317,11 @@ static int tilcdc_init(const struct drm_driver *ddrv, struct device *dev)
 
 	DBG("Maximum Pixel Clock Value %dKHz", priv->max_pixelclock);
 
+	if (variant == DA850_TILCDC)
+		priv->fifo_th = 16;
+	else
+		priv->fifo_th = 8;
+
 	ret = tilcdc_crtc_create(ddev);
 	if (ret < 0) {
 		dev_err(dev, "failed to create crtc\n");
@@ -598,8 +611,8 @@ static void tilcdc_pdev_shutdown(struct platform_device *pdev)
 }
 
 static const struct of_device_id tilcdc_of_match[] = {
-		{ .compatible = "ti,am33xx-tilcdc", },
-		{ .compatible = "ti,da850-tilcdc", },
+		{ .compatible = "ti,am33xx-tilcdc", .data = (void *)AM33XX_TILCDC},
+		{ .compatible = "ti,da850-tilcdc", .data = (void *)DA850_TILCDC},
 		{ },
 };
 MODULE_DEVICE_TABLE(of, tilcdc_of_match);
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_drv.h b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
index 3aba3a1155ba0..79078b4ae7393 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_drv.h
+++ b/drivers/gpu/drm/tilcdc/tilcdc_drv.h
@@ -61,6 +61,8 @@ struct tilcdc_drm_private {
 	 */
 	uint32_t max_width;
 
+	u32 fifo_th;
+
 	/* Supported pixel formats */
 	const uint32_t *pixelformats;
 	uint32_t num_pixelformats;

-- 
2.43.0