Re: [PATCH v16 4/4] drm/bridge: dw-hdmi: fix bus formats negotiation for 8 bit modes

[Neil Armstrong <narmstrong@baylibre.com>]

Hi,

On 02/03/2022 23:24, H. Nikolaus Schaller wrote:
> Hi Neil,
> 
>> Am 02.03.2022 um 15:34 schrieb Neil Armstrong <narmstrong@baylibre.com>:
>>
>> Hi,
>>
>>> (cross-checked: RGB mode still works if I force hdmi->sink_is_hdmi = false)
>>
>> I don't understand what's wrong, can you try to make the logic select MEDIA_BUS_FMT_YUV8_1X24 instead of DRM_COLOR_FORMAT_YCBCR422 ?
> 
> I have forced hdmi->sink_is_hdmi = false and replaced
> 
>   	/* Default 8bit RGB fallback */
> -	output_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
> +	output_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
> 
> And then screen remains black. MEDIA_BUS_FMT_RGB888_1X24 works.
> (MEDIA_BUS_FMT_VUY8_1X24 doesn't work either).
> 
> So this indicates that YUV conversion is not working properly. Maybe missing some special
> setup.
> 
> What I have to test if it works on a different monitor. Not that this specific panel
> (a 7 inch waveshare touch with HDMIinput) is buggy and reports YUV capabilities
> but does not handle them...
> 
> On the other hand this panel works on RasPi and OMAP5 (where I admit I do not know in
> which mode).

Pretty sure they don't support YUV HDMI output.

If you can try on a certified HDMI devices like a TV, it would here figuring out where comes the issue.

> 
>> If your CSC is broken, we'll need to disable it on your platform.
> 
> Indeed.
> 
> So it seems as if we need a mechanism to overwrite dw_hdmi_bridge_atomic_get_output_bus_fmts()
> in our ingenic-dw-hdmi platform specialization [1] to always return MEDIA_BUS_FMT_RGB888_1X24.
> 
> Or alternatively set sink_is_hdmi = false there (unfortunately there is no direct access to
> struct dw_hdmi in a specialization drivers).
> 
> Is this already possible or how can it be done?

It's not handled yet, but we may add the logic to handle the lack of CSC config bit and
add a glue config bit to override this like we already did for CEC.

I wrote an initial support to disable CSC (only compile-tested), could you try on your platform with setting disable_csc = 1 in your dw-hdmi glue code ?

================><=======================================
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 54d8fdad395f..d345166a69aa 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -158,6 +158,8 @@ struct dw_hdmi {
  	struct hdmi_data_info hdmi_data;
  	const struct dw_hdmi_plat_data *plat_data;

+	bool csc_available;		/* indicates if the CSC engine is usable */
+
  	int vic;

  	u8 edid[HDMI_EDID_LEN];
@@ -1009,9 +1011,10 @@ static int is_color_space_interpolation(struct dw_hdmi *hdmi)

  static bool is_csc_needed(struct dw_hdmi *hdmi)
  {
-	return is_color_space_conversion(hdmi) ||
-	       is_color_space_decimation(hdmi) ||
-	       is_color_space_interpolation(hdmi);
+	return hdmi->csc_available &&
+	       (is_color_space_conversion(hdmi) ||
+	        is_color_space_decimation(hdmi) ||
+	        is_color_space_interpolation(hdmi));
  }

  static void dw_hdmi_update_csc_coeffs(struct dw_hdmi *hdmi)
@@ -1064,6 +1067,9 @@ static void hdmi_video_csc(struct dw_hdmi *hdmi)
  	int interpolation = HDMI_CSC_CFG_INTMODE_DISABLE;
  	int decimation = 0;

+	if (!hdmi->csc_available)
+		return;
+
  	/* YCC422 interpolation to 444 mode */
  	if (is_color_space_interpolation(hdmi))
  		interpolation = HDMI_CSC_CFG_INTMODE_CHROMA_INT_FORMULA1;
@@ -2663,6 +2669,7 @@ static u32 *dw_hdmi_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
  					u32 output_fmt,
  					unsigned int *num_input_fmts)
  {
+	struct dw_hdmi *hdmi = bridge->driver_private;
  	u32 *input_fmts;
  	unsigned int i = 0;

@@ -2681,62 +2688,81 @@ static u32 *dw_hdmi_bridge_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
  	/* 8bit */
  	case MEDIA_BUS_FMT_RGB888_1X24:
  		input_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
-		input_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
+			input_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
+		}
  		break;
  	case MEDIA_BUS_FMT_YUV8_1X24:
  		input_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
-		input_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
+			input_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
+		}
  		break;
  	case MEDIA_BUS_FMT_UYVY8_1X16:
  		input_fmts[i++] = MEDIA_BUS_FMT_UYVY8_1X16;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV8_1X24;
+			input_fmts[i++] = MEDIA_BUS_FMT_RGB888_1X24;
+		}
  		break;

  	/* 10bit */
  	case MEDIA_BUS_FMT_RGB101010_1X30:
  		input_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV10_1X30;
-		input_fmts[i++] = MEDIA_BUS_FMT_UYVY10_1X20;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV10_1X30;
+			input_fmts[i++] = MEDIA_BUS_FMT_UYVY10_1X20;
+		}
  		break;
  	case MEDIA_BUS_FMT_YUV10_1X30:
  		input_fmts[i++] = MEDIA_BUS_FMT_YUV10_1X30;
-		input_fmts[i++] = MEDIA_BUS_FMT_UYVY10_1X20;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_UYVY10_1X20;
+			input_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
+		}
  		break;
  	case MEDIA_BUS_FMT_UYVY10_1X20:
  		input_fmts[i++] = MEDIA_BUS_FMT_UYVY10_1X20;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV10_1X30;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV10_1X30;
+			input_fmts[i++] = MEDIA_BUS_FMT_RGB101010_1X30;
+		}
  		break;

  	/* 12bit */
  	case MEDIA_BUS_FMT_RGB121212_1X36:
  		input_fmts[i++] = MEDIA_BUS_FMT_RGB121212_1X36;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV12_1X36;
-		input_fmts[i++] = MEDIA_BUS_FMT_UYVY12_1X24;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV12_1X36;
+			input_fmts[i++] = MEDIA_BUS_FMT_UYVY12_1X24;
+		}
  		break;
  	case MEDIA_BUS_FMT_YUV12_1X36:
  		input_fmts[i++] = MEDIA_BUS_FMT_YUV12_1X36;
-		input_fmts[i++] = MEDIA_BUS_FMT_UYVY12_1X24;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB121212_1X36;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_UYVY12_1X24;
+			input_fmts[i++] = MEDIA_BUS_FMT_RGB121212_1X36;
+		}
  		break;
  	case MEDIA_BUS_FMT_UYVY12_1X24:
  		input_fmts[i++] = MEDIA_BUS_FMT_UYVY12_1X24;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV12_1X36;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB121212_1X36;
+		if (hdmi->csc_available) {
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV12_1X36;
+			input_fmts[i++] = MEDIA_BUS_FMT_RGB121212_1X36;
+		}
  		break;

  	/* 16bit */
  	case MEDIA_BUS_FMT_RGB161616_1X48:
  		input_fmts[i++] = MEDIA_BUS_FMT_RGB161616_1X48;
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
+		if (hdmi->csc_available)
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
  		break;
  	case MEDIA_BUS_FMT_YUV16_1X48:
-		input_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
-		input_fmts[i++] = MEDIA_BUS_FMT_RGB161616_1X48;
+		if (hdmi->csc_available)
+			input_fmts[i++] = MEDIA_BUS_FMT_YUV16_1X48;
  		break;

  	/*YUV 4:2:0 */
@@ -2765,15 +2791,24 @@ static int dw_hdmi_bridge_atomic_check(struct drm_bridge *bridge,
  {
  	struct dw_hdmi *hdmi = bridge->driver_private;

-	hdmi->hdmi_data.enc_out_bus_format =
-			bridge_state->output_bus_cfg.format;
+	if (!hdmi->csc_available &&
+	    bridge_state->output_bus_cfg.format != bridge_state->input_bus_cfg.format) {
+		dev_warn(hdmi->dev, "different input format 0x%04x & output format 0x%04x while CSC isn't usable, fallback to safe format\n",
+			 bridge_state->input_bus_cfg.format,
+			 bridge_state->output_bus_cfg.format);
+		hdmi->hdmi_data.enc_out_bus_format = MEDIA_BUS_FMT_FIXED;
+		hdmi->hdmi_data.enc_in_bus_format = MEDIA_BUS_FMT_FIXED;
+	} else {
+		hdmi->hdmi_data.enc_out_bus_format =
+				bridge_state->output_bus_cfg.format;

-	hdmi->hdmi_data.enc_in_bus_format =
-			bridge_state->input_bus_cfg.format;
+		hdmi->hdmi_data.enc_in_bus_format =
+				bridge_state->input_bus_cfg.format;

-	dev_dbg(hdmi->dev, "input format 0x%04x, output format 0x%04x\n",
-		bridge_state->input_bus_cfg.format,
-		bridge_state->output_bus_cfg.format);
+		dev_dbg(hdmi->dev, "input format 0x%04x, output format 0x%04x\n",
+			bridge_state->input_bus_cfg.format,
+			bridge_state->output_bus_cfg.format);
+	}

  	return 0;
  }
@@ -3479,6 +3514,9 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
  		hdmi->cec = platform_device_register_full(&pdevinfo);
  	}

+	/* Get CSC useability from config0 register and permit override for platforms */
+	hdmi->csc_available = !plat_data->disable_csc || (config0 & HDMI_CONFIG0_CSC);
+
  	drm_bridge_add(&hdmi->bridge);

  	return hdmi;
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
index 1999db05bc3b..279722e4d189 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
@@ -541,6 +541,7 @@ enum {

  /* CONFIG0_ID field values */
  	HDMI_CONFIG0_I2S = 0x10,
+	HDMI_CONFIG0_CSC = 0x04,
  	HDMI_CONFIG0_CEC = 0x02,

  /* CONFIG1_ID field values */
diff --git a/include/drm/bridge/dw_hdmi.h b/include/drm/bridge/dw_hdmi.h
index 2a1f85f9a8a3..b2f689cbe864 100644
--- a/include/drm/bridge/dw_hdmi.h
+++ b/include/drm/bridge/dw_hdmi.h
@@ -157,6 +157,7 @@ struct dw_hdmi_plat_data {
  			     unsigned long mpixelclock);

  	unsigned int disable_cec : 1;
+	unsigned int disable_csc : 1;
  };

  struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev,
=================><==============================================================

Neil

> 
> BR and thanks,
> Nikolaus
> 
> [1]: https://lore.kernel.org/all/24a27226a22adf5f5573f013e5d7d89b0ec73664.1645895582.git.hns@goldelico.com/