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Message-ID: <20251016001038.13611-4-iam@lach.pw>
Date: Thu, 16 Oct 2025 02:10:39 +0200
From: Yaroslav Bolyukin <iam@...h.pw>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Maxime Ripard <mripard@...nel.org>,
Thomas Zimmermann <tzimmermann@...e.de>,
David Airlie <airlied@...il.com>,
Simona Vetter <simona@...ll.ch>
Cc: Harry Wentland <harry.wentland@....com>,
Leo Li <sunpeng.li@....com>,
Rodrigo Siqueira <siqueira@...lia.com>,
Alex Deucher <alexander.deucher@....com>,
Christian König <christian.koenig@....com>,
Wayne Lin <Wayne.Lin@....com>,
amd-gfx@...ts.freedesktop.org,
linux-kernel@...r.kernel.org,
dri-devel@...ts.freedesktop.org,
Yaroslav Bolyukin <iam@...h.pw>
Subject: [PATCH v4 1/2] drm/edid: parse DRM VESA dsc bpp target
As per DisplayID v2.0 Errata E9 spec "DSC pass-through timing support"
VESA vendor-specific data block may contain target DSC bits per pixel
fields
Signed-off-by: Yaroslav Bolyukin <iam@...h.pw>
---
drivers/gpu/drm/drm_displayid_internal.h | 8 ++++
drivers/gpu/drm/drm_edid.c | 61 ++++++++++++++++--------
include/drm/drm_connector.h | 6 +++
include/drm/drm_modes.h | 10 ++++
4 files changed, 64 insertions(+), 21 deletions(-)
diff --git a/drivers/gpu/drm/drm_displayid_internal.h b/drivers/gpu/drm/drm_displayid_internal.h
index 957dd0619f5c..d008a98994bb 100644
--- a/drivers/gpu/drm/drm_displayid_internal.h
+++ b/drivers/gpu/drm/drm_displayid_internal.h
@@ -97,6 +97,10 @@ struct displayid_header {
u8 ext_count;
} __packed;
+#define DISPLAYID_BLOCK_REV GENMASK(2, 0)
+#define DISPLAYID_BLOCK_PASSTHROUGH_TIMINGS_SUPPORT BIT(3)
+#define DISPLAYID_BLOCK_DESCRIPTOR_PAYLOAD_BYTES GENMASK(6, 4)
+
struct displayid_block {
u8 tag;
u8 rev;
@@ -144,12 +148,16 @@ struct displayid_formula_timing_block {
#define DISPLAYID_VESA_MSO_OVERLAP GENMASK(3, 0)
#define DISPLAYID_VESA_MSO_MODE GENMASK(6, 5)
+#define DISPLAYID_VESA_DSC_BPP_INT GENMASK(5, 0)
+#define DISPLAYID_VESA_DSC_BPP_FRACT GENMASK(3, 0)
struct displayid_vesa_vendor_specific_block {
struct displayid_block base;
u8 oui[3];
u8 data_structure_type;
u8 mso;
+ u8 dsc_bpp_int;
+ u8 dsc_bpp_fract;
} __packed;
/*
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index e2e85345aa9a..6e42e55b41f9 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -6524,8 +6524,8 @@ static void drm_get_monitor_range(struct drm_connector *connector,
info->monitor_range.min_vfreq, info->monitor_range.max_vfreq);
}
-static void drm_parse_vesa_mso_data(struct drm_connector *connector,
- const struct displayid_block *block)
+static void drm_parse_vesa_specific_block(struct drm_connector *connector,
+ const struct displayid_block *block)
{
struct displayid_vesa_vendor_specific_block *vesa =
(struct displayid_vesa_vendor_specific_block *)block;
@@ -6541,7 +6541,7 @@ static void drm_parse_vesa_mso_data(struct drm_connector *connector,
if (oui(vesa->oui[0], vesa->oui[1], vesa->oui[2]) != VESA_IEEE_OUI)
return;
- if (sizeof(*vesa) != sizeof(*block) + block->num_bytes) {
+ if (block->num_bytes < 5) {
drm_dbg_kms(connector->dev,
"[CONNECTOR:%d:%s] Unexpected VESA vendor block size\n",
connector->base.id, connector->name);
@@ -6564,28 +6564,40 @@ static void drm_parse_vesa_mso_data(struct drm_connector *connector,
break;
}
- if (!info->mso_stream_count) {
- info->mso_pixel_overlap = 0;
- return;
- }
+ info->mso_pixel_overlap = 0;
- info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);
- if (info->mso_pixel_overlap > 8) {
- drm_dbg_kms(connector->dev,
- "[CONNECTOR:%d:%s] Reserved MSO pixel overlap value %u\n",
- connector->base.id, connector->name,
- info->mso_pixel_overlap);
- info->mso_pixel_overlap = 8;
+ if (info->mso_stream_count) {
+ info->mso_pixel_overlap = FIELD_GET(DISPLAYID_VESA_MSO_OVERLAP, vesa->mso);
+ if (info->mso_pixel_overlap > 8) {
+ drm_dbg_kms(connector->dev,
+ "[CONNECTOR:%d:%s] Reserved MSO pixel overlap value %u\n",
+ connector->base.id, connector->name,
+ info->mso_pixel_overlap);
+ info->mso_pixel_overlap = 8;
+ }
}
drm_dbg_kms(connector->dev,
"[CONNECTOR:%d:%s] MSO stream count %u, pixel overlap %u\n",
connector->base.id, connector->name,
info->mso_stream_count, info->mso_pixel_overlap);
+
+ if (block->num_bytes < 7) {
+ /* DSC bpp is optional */
+ return;
+ }
+
+ info->dp_dsc_bpp = FIELD_GET(DISPLAYID_VESA_DSC_BPP_INT, vesa->dsc_bpp_int) << 4 |
+ FIELD_GET(DISPLAYID_VESA_DSC_BPP_FRACT, vesa->dsc_bpp_fract);
+
+ drm_dbg_kms(connector->dev,
+ "[CONNECTOR:%d:%s] DSC bits per pixel %u\n",
+ connector->base.id, connector->name,
+ info->dp_dsc_bpp);
}
-static void drm_update_mso(struct drm_connector *connector,
- const struct drm_edid *drm_edid)
+static void drm_update_vesa_specific_block(struct drm_connector *connector,
+ const struct drm_edid *drm_edid)
{
const struct displayid_block *block;
struct displayid_iter iter;
@@ -6593,7 +6605,7 @@ static void drm_update_mso(struct drm_connector *connector,
displayid_iter_edid_begin(drm_edid, &iter);
displayid_iter_for_each(block, &iter) {
if (block->tag == DATA_BLOCK_2_VENDOR_SPECIFIC)
- drm_parse_vesa_mso_data(connector, block);
+ drm_parse_vesa_specific_block(connector, block);
}
displayid_iter_end(&iter);
}
@@ -6630,6 +6642,7 @@ static void drm_reset_display_info(struct drm_connector *connector)
info->mso_stream_count = 0;
info->mso_pixel_overlap = 0;
info->max_dsc_bpp = 0;
+ info->dp_dsc_bpp = 0;
kfree(info->vics);
info->vics = NULL;
@@ -6753,7 +6766,7 @@ static void update_display_info(struct drm_connector *connector,
if (edid->features & DRM_EDID_FEATURE_RGB_YCRCB422)
info->color_formats |= DRM_COLOR_FORMAT_YCBCR422;
- drm_update_mso(connector, drm_edid);
+ drm_update_vesa_specific_block(connector, drm_edid);
out:
if (drm_edid_has_internal_quirk(connector, EDID_QUIRK_NON_DESKTOP)) {
@@ -6784,7 +6797,8 @@ static void update_display_info(struct drm_connector *connector,
static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *dev,
const struct displayid_detailed_timings_1 *timings,
- bool type_7)
+ bool type_7,
+ int rev)
{
struct drm_display_mode *mode;
unsigned int pixel_clock = (timings->pixel_clock[0] |
@@ -6805,6 +6819,10 @@ static struct drm_display_mode *drm_mode_displayid_detailed(struct drm_device *d
if (!mode)
return NULL;
+ if (type_7 && FIELD_GET(DISPLAYID_BLOCK_REV, rev) >= 1)
+ mode->dsc_passthrough_timings_support =
+ !!(rev & DISPLAYID_BLOCK_PASSTHROUGH_TIMINGS_SUPPORT);
+
/* resolution is kHz for type VII, and 10 kHz for type I */
mode->clock = type_7 ? pixel_clock : pixel_clock * 10;
mode->hdisplay = hactive;
@@ -6846,7 +6864,7 @@ static int add_displayid_detailed_1_modes(struct drm_connector *connector,
for (i = 0; i < num_timings; i++) {
struct displayid_detailed_timings_1 *timings = &det->timings[i];
- newmode = drm_mode_displayid_detailed(connector->dev, timings, type_7);
+ newmode = drm_mode_displayid_detailed(connector->dev, timings, type_7, block->rev);
if (!newmode)
continue;
@@ -6893,7 +6911,8 @@ static int add_displayid_formula_modes(struct drm_connector *connector,
struct drm_display_mode *newmode;
int num_modes = 0;
bool type_10 = block->tag == DATA_BLOCK_2_TYPE_10_FORMULA_TIMING;
- int timing_size = 6 + ((formula_block->base.rev & 0x70) >> 4);
+ int timing_size = 6 +
+ FIELD_GET(DISPLAYID_BLOCK_DESCRIPTOR_PAYLOAD_BYTES, formula_block->base.rev);
/* extended blocks are not supported yet */
if (timing_size != 6)
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 8f34f4b8183d..01640fcf7464 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -837,6 +837,12 @@ struct drm_display_info {
*/
u32 max_dsc_bpp;
+ /**
+ * @dp_dsc_bpp: DP Display-Stream-Compression (DSC) timing's target
+ * DSC bits per pixel in 6.4 fixed point format. 0 means undefined.
+ */
+ u16 dp_dsc_bpp;
+
/**
* @vics: Array of vics_len VICs. Internal to EDID parsing.
*/
diff --git a/include/drm/drm_modes.h b/include/drm/drm_modes.h
index b9bb92e4b029..312e5c03af9a 100644
--- a/include/drm/drm_modes.h
+++ b/include/drm/drm_modes.h
@@ -417,6 +417,16 @@ struct drm_display_mode {
*/
enum hdmi_picture_aspect picture_aspect_ratio;
+ /**
+ * @dsc_passthrough_timing_support:
+ *
+ * Indicates whether this mode timing descriptor is supported
+ * with specific target DSC bits per pixel only.
+ *
+ * VESA vendor-specific data block shall exist with the relevant
+ * DSC bits per pixel declaration when this flag is set to true.
+ */
+ bool dsc_passthrough_timings_support;
};
/**
--
2.51.0
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