Re: [PATCH v4 07/16] drm/dp_helper: Add helpers to configure PCONs RGB-YCbCr Conversion

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Hi Uma Shankar,

Thanks for the comments and suggestions.

Please find my response inline.

On 12/13/2020 12:40 PM, Shankar, Uma wrote:

-----Original Message-----
From: Nautiyal, Ankit K <ankit.k.nautiyal@xxxxxxxxx>
Sent: Tuesday, December 8, 2020 1:22 PM
To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx; Shankar, Uma <uma.shankar@xxxxxxxxx>;
airlied@xxxxxxxx; jani.nikula@xxxxxxxxxxxxxxx; ville.syrjala@xxxxxxxxxxxxxxx;
Kulkarni, Vandita <vandita.kulkarni@xxxxxxxxx>; Sharma, Swati2
<swati2.sharma@xxxxxxxxx>
Subject: [PATCH v4 07/16] drm/dp_helper: Add helpers to configure PCONs RGB-
YCbCr Conversion

DP Specification for DP2.0 to HDMI2.1 Pcon specifies support for conversion of
colorspace from RGB to YCbCr.
https://groups.vesa.org/wg/DP/document/previewpdf/15651

This patch adds the relavant registers and helper functions to get the capability
and set the color conversion bits for rgb->ycbcr conversion through PCON.

Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
---
  drivers/gpu/drm/drm_dp_helper.c | 59 +++++++++++++++++++++++++++++++++
  include/drm/drm_dp_helper.h     | 10 +++++-
  2 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c
b/drivers/gpu/drm/drm_dp_helper.c index d0626f57f99c..344662d5c295 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -949,6 +949,35 @@ bool
drm_dp_downstream_444_to_420_conversion(const u8
dpcd[DP_RECEIVER_CAP_SIZE]  }
EXPORT_SYMBOL(drm_dp_downstream_444_to_420_conversion);

+/**
+ * drm_dp_downstream_rgb_to_ycbcr_conversion() - determine downstream
facing port
+ *                                               RGB->YCbCr conversion capability
+ * @dpcd: DisplayPort configuration data
+ * @port_cap: downstream facing port capabilities
+ *
+ * Returns: whether the downstream facing port can convert RGB->YCbCr
+*/ bool drm_dp_downstream_rgb_to_ycbcr_conversion(const u8
+dpcd[DP_RECEIVER_CAP_SIZE],
+					       const u8 port_cap[4])
+{
+	if (!drm_dp_is_branch(dpcd))
+		return false;
+
+	if (dpcd[DP_DPCD_REV] < 0x13)
+		return false;
+
+	switch (port_cap[0] & DP_DS_PORT_TYPE_MASK) {
+	case DP_DS_PORT_TYPE_HDMI:
+		if ((dpcd[DP_DOWNSTREAMPORT_PRESENT] &
DP_DETAILED_CAP_INFO_AVAILABLE) == 0)
+			return false;
+
+		return port_cap[3] & DP_DS_HDMI_BT601_RGB_YCBCR_CONV;
I guess there are other conversions also possible, like BT709 and 2020. Update those
as well here.


Yes you are right. I will modify the function to take as input colorspace, also and

the function will be returning true, if the rgb->ycbcr conversion for the given colorspace is supported.



+	default:
+		return false;
+	}
+}
+EXPORT_SYMBOL(drm_dp_downstream_rgb_to_ycbcr_conversion);
+
  /**
   * drm_dp_downstream_mode() - return a mode for downstream facing port
   * @dev: DRM device
@@ -3140,3 +3169,33 @@ int drm_dp_pcon_pps_override_param(struct
drm_dp_aux *aux, u8 pps_param[6])
  	return 0;
  }
  EXPORT_SYMBOL(drm_dp_pcon_pps_override_param);
+
+/*
+ * drm_dp_pcon_convert_rgb_to_ycbcr() - Configure the PCon to convert
+RGB to Ycbcr
+ * @aux: displayPort AUX channel
+ * @color_spc: Color space conversion type
+ *
+ * Returns 0 on success, else returns negative error code.
+ */
+int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8
+color_spc) {
+	int ret;
+	u8 buf;
+
+	if (color_spc != DP_CONVERSION_BT601_RGB_YCBCR_ENABLE ||
+	    color_spc != DP_CONVERSION_BT709_RGB_YCBCR_ENABLE ||
+	    color_spc != DP_CONVERSION_BT2020_RGB_YCBCR_ENABLE)
+		return -EINVAL;
Yeah this is wrong, fix it.

Agreed. Will fix this in next version of the patch.


+
+	ret = drm_dp_dpcd_readb(aux, DP_PROTOCOL_CONVERTER_CONTROL_2,
&buf);
+	if (ret < 0)
+		return ret;
+
+	buf |= color_spc;
+	ret = drm_dp_dpcd_writeb(aux,
DP_PROTOCOL_CONVERTER_CONTROL_2, buf);
+	if (ret < 0)
+		return ret;
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_dp_pcon_convert_rgb_to_ycbcr);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index
347b4e1a55b4..1b3d54ed7a78 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -431,6 +431,9 @@ struct drm_device;
  # define DP_DS_HDMI_YCBCR420_PASS_THROUGH   (1 << 2)
  # define DP_DS_HDMI_YCBCR444_TO_422_CONV    (1 << 3)
  # define DP_DS_HDMI_YCBCR444_TO_420_CONV    (1 << 4)
+# define DP_DS_HDMI_BT601_RGB_YCBCR_CONV    (1 << 5)
+# define DP_DS_HDMI_BT709_RGB_YCBCR_CONV    (1 << 6)
+# define DP_DS_HDMI_BT2020_RGB_YCBCR_CONV   (1 << 7)
I think it would be good to mention the location in spec (section or table),
will make it easier to understand/review by directly going to relevant sections in spec.

This is still Draft 1 of the spec: VESA DP-to-HDMI PCON Specification Standalone Document. Link in the commit message.

I will mention the current Section and Table no. nevertheless in the next version of the patch.

Thanks & Regards,

Ankit

  #define DP_MAX_DOWNSTREAM_PORTS		    0x10

@@ -1217,7 +1220,9 @@ struct drm_device;
  # define DP_PCON_ENC_PPS_OVERRIDE_DISABLED      0
  # define DP_PCON_ENC_PPS_OVERRIDE_EN_PARAMS     1
  # define DP_PCON_ENC_PPS_OVERRIDE_EN_BUFFER     2
-
+# define DP_CONVERSION_BT601_RGB_YCBCR_ENABLE  (1 << 4) # define
+DP_CONVERSION_BT709_RGB_YCBCR_ENABLE  (1 << 5) # define
+DP_CONVERSION_BT2020_RGB_YCBCR_ENABLE (1 << 6)

  /* PCON Downstream HDMI ERROR Status per Lane */
  #define DP_PCON_HDMI_ERROR_STATUS_LN0          0x3037
@@ -2178,5 +2183,8 @@ int drm_dp_pcon_dsc_bpp_incr(const u8
pcon_dsc_dpcd[DP_PCON_DSC_ENCODER_CAP_SIZE
  int drm_dp_pcon_pps_default(struct drm_dp_aux *aux);  int
drm_dp_pcon_pps_override_buf(struct drm_dp_aux *aux, u8 pps_buf[128]);  int
drm_dp_pcon_pps_override_param(struct drm_dp_aux *aux, u8 pps_param[6]);
+bool drm_dp_downstream_rgb_to_ycbcr_conversion(const u8
dpcd[DP_RECEIVER_CAP_SIZE],
+					       const u8 port_cap[4]);
+int drm_dp_pcon_convert_rgb_to_ycbcr(struct drm_dp_aux *aux, u8
+color_spc);

  #endif /* _DRM_DP_HELPER_H_ */
--
2.17.1
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