drm/displayid: add quirk to ignore DisplayID checksum errors

Add a mechanism for DisplayID specific quirks, and add the first quirk
to ignore DisplayID section checksum errors.

It would be quite inconvenient to pass existing EDID quirks from
drm_edid.c for DisplayID parsing. Not all places doing DisplayID
iteration have the quirks readily available, and would have to pass it
in all places. Simply add a separate array of DisplayID specific EDID
quirks. We do end up checking it every time we iterate DisplayID blocks,
but hopefully the number of quirks remains small.

There are a few laptop models with DisplayID checksum failures, leading
to higher refresh rates only present in the DisplayID blocks being
ignored. Add a quirk for the panel in the machines.

Reported-by: Tiago Martins Araújo <tiago.martins.araujo@gmail.com>
Closes: https://lore.kernel.org/r/CACRbrPGvLP5LANXuFi6z0S7XMbAG4X5y2YOLBDxfOVtfGGqiKQ@mail.gmail.com
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14703
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Tested-by: Tiago Martins Araújo <tiago.martins.araujo@gmail.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/c04d81ae648c5f21b3f5b7953f924718051f2798.1761681968.git.jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Author: jnikula

drivers/gpu/drm/drm_displayid.c

@@ -9,6 +9,34 @@
 #include "drm_crtc_internal.h"
 #include "drm_displayid_internal.h"
 
+enum {
+	QUIRK_IGNORE_CHECKSUM,
+};
+
+struct displayid_quirk {
+	const struct drm_edid_ident ident;
+	u8 quirks;
+};
+
+static const struct displayid_quirk quirks[] = {
+	{
+		.ident = DRM_EDID_IDENT_INIT('C', 'S', 'O', 5142, "MNE007ZA1-5"),
+		.quirks = BIT(QUIRK_IGNORE_CHECKSUM),
+	},
+};
+
+static u8 get_quirks(const struct drm_edid *drm_edid)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(quirks); i++) {
+		if (drm_edid_match(drm_edid, &quirks[i].ident))
+			return quirks[i].quirks;
+	}
+
+	return 0;
+}
+
 static const struct displayid_header *
 displayid_get_header(const u8 *displayid, int length, int index)
 {
@@ -23,7 +51,7 @@ displayid_get_header(const u8 *displayid, int length, int index)
 }
 
 static const struct displayid_header *
-validate_displayid(const u8 *displayid, int length, int idx)
+validate_displayid(const u8 *displayid, int length, int idx, bool ignore_checksum)
 {
 	int i, dispid_length;
 	u8 csum = 0;
@@ -41,8 +69,11 @@ validate_displayid(const u8 *displayid, int length, int idx)
 	for (i = 0; i < dispid_length; i++)
 		csum += displayid[idx + i];
 	if (csum) {
-		DRM_NOTE("DisplayID checksum invalid, remainder is %d\n", csum);
-		return ERR_PTR(-EINVAL);
+		DRM_NOTE("DisplayID checksum invalid, remainder is %d%s\n", csum,
+			 ignore_checksum ? " (ignoring)" : "");
+
+		if (!ignore_checksum)
+			return ERR_PTR(-EINVAL);
 	}
 
 	return base;
@@ -52,6 +83,7 @@ static const u8 *find_next_displayid_extension(struct displayid_iter *iter)
 {
 	const struct displayid_header *base;
 	const u8 *displayid;
+	bool ignore_checksum = iter->quirks & BIT(QUIRK_IGNORE_CHECKSUM);
 
 	displayid = drm_edid_find_extension(iter->drm_edid, DISPLAYID_EXT, &iter->ext_index);
 	if (!displayid)
@@ -61,7 +93,7 @@ static const u8 *find_next_displayid_extension(struct displayid_iter *iter)
 	iter->length = EDID_LENGTH - 1;
 	iter->idx = 1;
 
-	base = validate_displayid(displayid, iter->length, iter->idx);
+	base = validate_displayid(displayid, iter->length, iter->idx, ignore_checksum);
 	if (IS_ERR(base))
 		return NULL;
 
@@ -76,6 +108,7 @@ void displayid_iter_edid_begin(const struct drm_edid *drm_edid,
 	memset(iter, 0, sizeof(*iter));
 
 	iter->drm_edid = drm_edid;
+	iter->quirks = get_quirks(drm_edid);
 }
 
 static const struct displayid_block *

drivers/gpu/drm/drm_displayid_internal.h

@@ -167,6 +167,8 @@ struct displayid_iter {
 
 	u8 version;
 	u8 primary_use;
+
+	u8 quirks;
 };
 
 void displayid_iter_edid_begin(const struct drm_edid *drm_edid,