[kernel-vanilla] Add patch for DP++ adapter detection

2 files changed, 99 insertions, 1 deletions

diff --git a/core/modules/kernel-vanilla/module.build b/core/modules/kernel-vanilla/module.build
index eb43e586..ec40e649 100644
--- a/core/modules/kernel-vanilla/module.build
+++ b/core/modules/kernel-vanilla/module.build
@@ -79,7 +79,7 @@ fetch_kernel_source() {
 	# Other patches
 	local patch
 	cde "$MODULE_WORK_DIR/ksrc"
-	for patch in "${MODULE_DIR}/patches/"*; do
+	for patch in "${MODULE_DIR}/patches/"*${TARGET_KERNEL_SHORT%.*}*; do
 		[ -f "$patch" ] || continue
 		grep -q -F "$patch" "patches-done" && continue
 		pinfo "Applying $(basename "$patch")"
diff --git a/core/modules/kernel-vanilla/patches/dp-detect-5.15.patch b/core/modules/kernel-vanilla/patches/dp-detect-5.15.patch
new file mode 100644
index 00000000..eaf0c9a0
--- /dev/null
+++ b/core/modules/kernel-vanilla/patches/dp-detect-5.15.patch
@@ -0,0 +1,98 @@
+diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+index 3ea53bb67..6147da983 100644
+--- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
++++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
+@@ -63,23 +63,42 @@
+ ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
+ 			      u8 offset, void *buffer, size_t size)
+ {
++	int ret;
++	u8 zero = 0;
++	char *tmpbuf;
++	/*
++	 * As sub-addressing is not supported by all adaptors,
++	 * always explicitly read from the start and discard
++	 * any bytes that come before the requested offset.
++	 * This way, no matter whether the adaptor supports it
++	 * or not, we'll end up reading the proper data.
++	 */
+ 	struct i2c_msg msgs[] = {
+ 		{
+ 			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
+ 			.flags = 0,
+ 			.len = 1,
+-			.buf = &offset,
++			.buf = &zero,
+ 		},
+ 		{
+ 			.addr = DP_DUAL_MODE_SLAVE_ADDRESS,
+ 			.flags = I2C_M_RD,
+-			.len = size,
+-			.buf = buffer,
++			.len = size + offset,
++			.buf = NULL,
+ 		},
+ 	};
+-	int ret;
+ 
++	tmpbuf = kmalloc(size + offset, GFP_KERNEL);
++	if (!tmpbuf)
++		return -ENOMEM;
++
++	msgs[1].buf = tmpbuf;
+ 	ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
++	if (ret == ARRAY_SIZE(msgs))
++		memcpy(buffer, tmpbuf + offset, size);
++
++	kfree(tmpbuf);
++
+ 	if (ret < 0)
+ 		return ret;
+ 	if (ret != ARRAY_SIZE(msgs))
+@@ -208,18 +227,6 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(const struct drm_device *dev,
+ 	if (ret)
+ 		return DRM_DP_DUAL_MODE_UNKNOWN;
+ 
+-	/*
+-	 * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
+-	 * the offset but ignore it, and instead they just always return
+-	 * data from the start of the HDMI ID buffer. So for a broken
+-	 * type 1 HDMI adaptor a single byte read will always give us
+-	 * 0x44, and for a type 1 DVI adaptor it should give 0x00
+-	 * (assuming it implements any registers). Fortunately neither
+-	 * of those values will match the type 2 signature of the
+-	 * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
+-	 * the type 2 adaptor detection safely even in the presence
+-	 * of broken type 1 adaptors.
+-	 */
+ 	ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
+ 				    &adaptor_id, sizeof(adaptor_id));
+ 	drm_dbg_kms(dev, "DP dual mode adaptor ID: %02x (err %zd)\n", adaptor_id, ret);
+@@ -233,11 +240,10 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(const struct drm_device *dev,
+ 				return DRM_DP_DUAL_MODE_TYPE2_DVI;
+ 		}
+ 		/*
+-		 * If neither a proper type 1 ID nor a broken type 1 adaptor
+-		 * as described above, assume type 1, but let the user know
+-		 * that we may have misdetected the type.
++		 * If not a proper type 1 ID, still assume type 1, but let
++		 * the user know that we may have misdetected the type.
+ 		 */
+-		if (!is_type1_adaptor(adaptor_id) && adaptor_id != hdmi_id[0])
++		if (!is_type1_adaptor(adaptor_id))
+ 			drm_err(dev, "Unexpected DP dual mode adaptor ID %02x\n", adaptor_id);
+ 
+ 	}
+@@ -343,10 +349,8 @@ EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);
+  * @enable: enable (as opposed to disable) the TMDS output buffers
+  *
+  * Set the state of the TMDS output buffers in the adaptor. For
+- * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
+- * some type 1 adaptors have problems with registers (see comments
+- * in drm_dp_dual_mode_detect()) we avoid touching the register,
+- * making this function a no-op on type 1 adaptors.
++ * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register.
++ * Type1 adaptors do not support any register writes.
+  *
+  * Returns:
+  * 0 on success, negative error code on failure