drm: Add support for DP 1.4 Compliance edid corruption test

Unlike DP 1.2 edid corruption test, DP 1.4 requires to calculate
real CRC value of the last edid data block, and write it back.
Current edid CRC calculates routine adds the last CRC byte,
and check if non-zero.

This behavior is not accurate; actually, we need to return
the actual CRC value when corruption is detected.
This commit changes this issue by returning the calculated CRC,
and initiate the required sequence.

Change since v7
- Fix for CI.CHECKPATCH

Change since v6
- Add return check

Change since v5
- Obtain real CRC value before dumping bad edid

Change since v4
- Fix for CI.CHECKPATCH

Change since v3
- Fix a minor typo.

Change since v2
- Rewrite checksum computation routine to avoid duplicated code.
- Rename to avoid confusion.

Change since v1
- Have separate routine for returning real CRC.

Signed-off-by: Jerry (Fangzhi) Zuo <Jerry.Zuo@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211160832.24259-1-Jerry.Zuo@amd.com

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index f629fc5494a435873fe01b3e21d0e0cd131cf992..43e9f1968af4cc2ad80f4eb84c868ae0a192f52f 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -351,6 +351,65 @@ int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
 }
 EXPORT_SYMBOL(drm_dp_dpcd_read_link_status);
 
+/**
+ * drm_dp_send_real_edid_checksum() - send back real edid checksum value
+ * @aux: DisplayPort AUX channel
+ * @real_edid_checksum: real edid checksum for the last block
+ *
+ * Returns:
+ * True on success
+ */
+bool drm_dp_send_real_edid_checksum(struct drm_dp_aux *aux,
+                                   u8 real_edid_checksum)
+{
+       u8 link_edid_read = 0, auto_test_req = 0, test_resp = 0;
+
+       if (drm_dp_dpcd_read(aux, DP_DEVICE_SERVICE_IRQ_VECTOR,
+                            &auto_test_req, 1) < 1) {
+               DRM_ERROR("DPCD failed read at register 0x%x\n",
+                         DP_DEVICE_SERVICE_IRQ_VECTOR);
+               return false;
+       }
+       auto_test_req &= DP_AUTOMATED_TEST_REQUEST;
+
+       if (drm_dp_dpcd_read(aux, DP_TEST_REQUEST, &link_edid_read, 1) < 1) {
+               DRM_ERROR("DPCD failed read at register 0x%x\n",
+                         DP_TEST_REQUEST);
+               return false;
+       }
+       link_edid_read &= DP_TEST_LINK_EDID_READ;
+
+       if (!auto_test_req || !link_edid_read) {
+               DRM_DEBUG_KMS("Source DUT does not support TEST_EDID_READ\n");
+               return false;
+       }
+
+       if (drm_dp_dpcd_write(aux, DP_DEVICE_SERVICE_IRQ_VECTOR,
+                             &auto_test_req, 1) < 1) {
+               DRM_ERROR("DPCD failed write at register 0x%x\n",
+                         DP_DEVICE_SERVICE_IRQ_VECTOR);
+               return false;
+       }
+
+       /* send back checksum for the last edid extension block data */
+       if (drm_dp_dpcd_write(aux, DP_TEST_EDID_CHECKSUM,
+                             &real_edid_checksum, 1) < 1) {
+               DRM_ERROR("DPCD failed write at register 0x%x\n",
+                         DP_TEST_EDID_CHECKSUM);
+               return false;
+       }
+
+       test_resp |= DP_TEST_EDID_CHECKSUM_WRITE;
+       if (drm_dp_dpcd_write(aux, DP_TEST_RESPONSE, &test_resp, 1) < 1) {
+               DRM_ERROR("DPCD failed write at register 0x%x\n",
+                         DP_TEST_RESPONSE);
+               return false;
+       }
+
+       return true;
+}
+EXPORT_SYMBOL(drm_dp_send_real_edid_checksum);
+
 /**
  * drm_dp_downstream_max_clock() - extract branch device max
  *                                 pixel rate for legacy VGA

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 99769d6c9f8462e25d189c78df3990b8519b7b79..1fcec5f4c3ec2c8fc24b4170426aa33694eab110 100644 (file)
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -1590,11 +1590,22 @@ static int validate_displayid(u8 *displayid, int length, int idx);
 static int drm_edid_block_checksum(const u8 *raw_edid)
 {
        int i;
-       u8 csum = 0;
-       for (i = 0; i < EDID_LENGTH; i++)
+       u8 csum = 0, crc = 0;
+
+       for (i = 0; i < EDID_LENGTH - 1; i++)
                csum += raw_edid[i];
 
-       return csum;
+       crc = 0x100 - csum;
+
+       return crc;
+}
+
+static bool drm_edid_block_checksum_diff(const u8 *raw_edid, u8 real_checksum)
+{
+       if (raw_edid[EDID_LENGTH - 1] != real_checksum)
+               return true;
+       else
+               return false;
 }
 
 static bool drm_edid_is_zero(const u8 *in_edid, int length)
@@ -1652,7 +1663,7 @@ bool drm_edid_block_valid(u8 *raw_edid, int block, bool print_bad_edid,
        }
 
        csum = drm_edid_block_checksum(raw_edid);
-       if (csum) {
+       if (drm_edid_block_checksum_diff(raw_edid, csum)) {
                if (edid_corrupt)
                        *edid_corrupt = true;
 
@@ -1793,6 +1804,11 @@ static void connector_bad_edid(struct drm_connector *connector,
                               u8 *edid, int num_blocks)
 {
        int i;
+       u8 num_of_ext = edid[0x7e];
+
+       /* Calculate real checksum for the last edid extension block data */
+       connector->real_edid_checksum =
+               drm_edid_block_checksum(edid + num_of_ext * EDID_LENGTH);
 
        if (connector->bad_edid_counter++ && !drm_debug_enabled(DRM_UT_KMS))
                return;

diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 2113500b4075d93b9cf12e747f16f5180b410950..b3815371c271dfa95689b33e98586354b272b025 100644 (file)
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -1357,6 +1357,12 @@ struct drm_connector {
         * rev1.1 4.2.2.6
         */
        bool edid_corrupt;
+       /**
+        * @real_edid_checksum: real edid checksum for corrupted edid block.
+        * Required in Displayport 1.4 compliance testing
+        * rev1.1 4.2.2.6
+        */
+       u8 real_edid_checksum;
 
        /** @debugfs_entry: debugfs directory for this connector */
        struct dentry *debugfs_entry;

diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 127d6e1d3338d9aed650878479cc0daceacfcac1..957a3d00ee052c6231cb57f527cc2771836e2dc3 100644 (file)
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1459,6 +1459,9 @@ static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux,
 int drm_dp_dpcd_read_link_status(struct drm_dp_aux *aux,
                                 u8 status[DP_LINK_STATUS_SIZE]);
 
+bool drm_dp_send_real_edid_checksum(struct drm_dp_aux *aux,
+                                   u8 real_edid_checksum);
+
 int drm_dp_downstream_max_clock(const u8 dpcd[DP_RECEIVER_CAP_SIZE],
                                const u8 port_cap[4]);
 int drm_dp_downstream_max_bpc(const u8 dpcd[DP_RECEIVER_CAP_SIZE],