Commit 18a9cbbe authored by Jani Nikula's avatar Jani Nikula
Browse files

drm/edid: parse the DisplayID v2.0 VESA vendor block for MSO 



The VESA Organization Vendor-Specific Data Block, defined in VESA
DisplayID Standard v2.0, specifies the eDP Multi-SST Operation (MSO)
stream count and segment pixel overlap.

DisplayID v1.3 has Appendix B: DisplayID as an EDID Extension,
describing how DisplayID sections may be embedded in EDID extension
blocks. DisplayID v2.0 does not have such a section, perhaps implying
that DisplayID v2.0 data should not be included in EDID extensions, but
rather in a "pure" DisplayID structure at its own DDC address pair
A4h/A5h, as described in VESA E-DDC Standard v1.3 chapter 3.

However, in practice, displays out in the field have embedded DisplayID
v2.0 data blocks in EDID extensions, including, in particular, some eDP
MSO displays, where a pure DisplayID structure is not available at all.

Parse the MSO data from the DisplayID data block. Do it as part of
drm_add_display_info(), extending it to parse also DisplayID data to
avoid requiring extra calls to update the information.

v2: Check for VESA OUI (Ville)

Reviewed-by: default avatarUma Shankar <uma.shankar@intel.com>
Acked-by: default avatarMaxime Ripard <maxime@cerno.tech>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/73ca2887e7b37880690f5c9ba4594c9cd1170669.1630419362.git.jani.nikula@intel.com
parent 37eab1fe

drivers/gpu/drm/drm_edid.c

+72 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
 * DEALINGS IN THE SOFTWARE.

 */



#include <linux/bitfield.h>

#include <linux/hdmi.h>

#include <linux/i2c.h>

#include <linux/kernel.h>
@@ -5145,6 +5146,71 @@ void drm_get_monitor_range(struct drm_connector *connector, 
		      info->monitor_range.max_vfreq);

}



static void drm_parse_vesa_mso_data(struct drm_connector *connector,

				    const struct displayid_block *block)

{

	struct displayid_vesa_vendor_specific_block *vesa =

		(struct displayid_vesa_vendor_specific_block *)block;

	struct drm_display_info *info = &connector->display_info;



	if (block->num_bytes < 3) {

		drm_dbg_kms(connector->dev, "Unexpected vendor block size %u\n",

			    block->num_bytes);

		return;

	}



	if (oui(vesa->oui[0], vesa->oui[1], vesa->oui[2]) != VESA_IEEE_OUI)

		return;



	if (sizeof(*vesa) != sizeof(*block) + block->num_bytes) {

		drm_dbg_kms(connector->dev, "Unexpected VESA vendor block size\n");

		return;

	}



	switch (FIELD_GET(DISPLAYID_VESA_MSO_MODE, vesa->mso)) {

	default:

		drm_dbg_kms(connector->dev, "Reserved MSO mode value\n");

		fallthrough;

	case 0:

		info->mso_stream_count = 0;

		break;

	case 1:

		info->mso_stream_count = 2; /* 2 or 4 links */

		break;

	case 2:

		info->mso_stream_count = 4; /* 4 links */

		break;

	}



	if (!info->mso_stream_count) {

		info->mso_pixel_overlap = 0;

		return;

	}



	info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);

	if (info->mso_pixel_overlap > 8) {

		drm_dbg_kms(connector->dev, "Reserved MSO pixel overlap value %u\n",

			    info->mso_pixel_overlap);

		info->mso_pixel_overlap = 8;

	}



	drm_dbg_kms(connector->dev, "MSO stream count %u, pixel overlap %u\n",

		    info->mso_stream_count, info->mso_pixel_overlap);

}



static void drm_update_mso(struct drm_connector *connector, const struct edid *edid)

{

	const struct displayid_block *block;

	struct displayid_iter iter;



	displayid_iter_edid_begin(edid, &iter);

	displayid_iter_for_each(block, &iter) {

		if (block->tag == DATA_BLOCK_2_VENDOR_SPECIFIC)

			drm_parse_vesa_mso_data(connector, block);

	}

	displayid_iter_end(&iter);

}



/* A connector has no EDID information, so we've got no EDID to compute quirks from. Reset

 * all of the values which would have been set from EDID

 */
@@ -5168,6 +5234,9 @@ drm_reset_display_info(struct drm_connector *connector) 


	info->non_desktop = 0;

	memset(&info->monitor_range, 0, sizeof(info->monitor_range));



	info->mso_stream_count = 0;

	info->mso_pixel_overlap = 0;

}



u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edid)
@@ -5246,6 +5315,9 @@ u32 drm_add_display_info(struct drm_connector *connector, const struct edid *edi 
		info->color_formats |= DRM_COLOR_FORMAT_YCRCB444;

	if (edid->features & DRM_EDID_FEATURE_RGB_YCRCB422)

		info->color_formats |= DRM_COLOR_FORMAT_YCRCB422;



	drm_update_mso(connector, edid);



	return quirks;

}

include/drm/drm_connector.h

+12 −0
Original line number Diff line number Diff line
@@ -590,6 +590,18 @@ struct drm_display_info { 
	 * @monitor_range: Frequency range supported by monitor range descriptor

	 */

	struct drm_monitor_range_info monitor_range;



	/**

	 * @mso_stream_count: eDP Multi-SST Operation (MSO) stream count from

	 * the DisplayID VESA vendor block. 0 for conventional Single-Stream

	 * Transport (SST), or 2 or 4 MSO streams.

	 */

	u8 mso_stream_count;



	/**

	 * @mso_pixel_overlap: eDP MSO segment pixel overlap, 0-8 pixels.

	 */

	u8 mso_pixel_overlap;

};



int drm_display_info_set_bus_formats(struct drm_display_info *info,

include/drm/drm_displayid.h

+13 −0
Original line number Diff line number Diff line
@@ -23,9 +23,12 @@ 
#define DRM_DISPLAYID_H



#include <linux/types.h>

#include <linux/bits.h>



struct edid;



#define VESA_IEEE_OUI				0x3a0292



/* DisplayID Structure versions */

#define DISPLAY_ID_STRUCTURE_VER_12		0x12

#define DISPLAY_ID_STRUCTURE_VER_20		0x20
@@ -126,6 +129,16 @@ struct displayid_detailed_timing_block { 
	struct displayid_detailed_timings_1 timings[];

};



#define DISPLAYID_VESA_MSO_OVERLAP	GENMASK(3, 0)

#define DISPLAYID_VESA_MSO_MODE		GENMASK(6, 5)



struct displayid_vesa_vendor_specific_block {

	struct displayid_block base;

	u8 oui[3];

	u8 data_structure_type;

	u8 mso;

} __packed;



/* DisplayID iteration */

struct displayid_iter {

	const struct edid *edid;