drm/amd/display: fix read errors pertaining to dp_lttpr_status_show()

Currently, it is likely that we will read the relevant LTTPR caps after
link training has completed (which can cause garbage data to be read),
however according to the DP 2.0 spec that should be done before link
training has commenced. So, instead of reading the registers on demand,
use the values provided to us by DC.

Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Hamza Mahfooz <hamza.mahfooz@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_debugfs.c

@@ -36,6 +36,7 @@
 #include "dsc.h"
 #include "link_hwss.h"
 #include "dc/dc_dmub_srv.h"
+#include "link/protocols/link_dp_capability.h"
 
 #ifdef CONFIG_DRM_AMD_SECURE_DISPLAY
 #include "amdgpu_dm_psr.h"
@@ -418,67 +419,38 @@ static ssize_t dp_phy_settings_read(struct file *f, char __user *buf,
 	return result;
 }
 
-static int dp_lttpr_status_show(struct seq_file *m, void *d)
+static int dp_lttpr_status_show(struct seq_file *m, void *unused)
 {
-	char *data;
-	struct amdgpu_dm_connector *connector = file_inode(m->file)->i_private;
-	struct dc_link *link = connector->dc_link;
-	uint32_t read_size = 1;
-	uint8_t repeater_count = 0;
+	struct drm_connector *connector = m->private;
+	struct amdgpu_dm_connector *aconnector =
+		to_amdgpu_dm_connector(connector);
+	struct dc_lttpr_caps caps = aconnector->dc_link->dpcd_caps.lttpr_caps;
 
-	data = kzalloc(read_size, GFP_KERNEL);
-	if (!data)
-		return 0;
+	if (connector->status != connector_status_connected)
+		return -ENODEV;
 
-	dm_helpers_dp_read_dpcd(link->ctx, link, 0xF0002, data, read_size);
+	seq_printf(m, "phy repeater count: %u (raw: 0x%x)\n",
+		   dp_parse_lttpr_repeater_count(caps.phy_repeater_cnt),
+		   caps.phy_repeater_cnt);
 
-	switch ((uint8_t)*data) {
-	case 0x80:
-		repeater_count = 1;
-		break;
-	case 0x40:
-		repeater_count = 2;
-		break;
-	case 0x20:
-		repeater_count = 3;
-		break;
-	case 0x10:
-		repeater_count = 4;
-		break;
-	case 0x8:
-		repeater_count = 5;
-		break;
-	case 0x4:
-		repeater_count = 6;
-		break;
-	case 0x2:
-		repeater_count = 7;
+	seq_puts(m, "phy repeater mode: ");
+
+	switch (caps.mode) {
+	case DP_PHY_REPEATER_MODE_TRANSPARENT:
+		seq_puts(m, "transparent");
 		break;
-	case 0x1:
-		repeater_count = 8;
+	case DP_PHY_REPEATER_MODE_NON_TRANSPARENT:
+		seq_puts(m, "non-transparent");
 		break;
-	case 0x0:
-		repeater_count = 0;
+	case 0x00:
+		seq_puts(m, "non lttpr");
 		break;
 	default:
-		repeater_count = (uint8_t)*data;
+		seq_printf(m, "read error (raw: 0x%x)", caps.mode);
 		break;
 	}
 
-	seq_printf(m, "phy repeater count: %d\n", repeater_count);
-
-	dm_helpers_dp_read_dpcd(link->ctx, link, 0xF0003, data, read_size);
-
-	if ((uint8_t)*data == 0x55)
-		seq_printf(m, "phy repeater mode: transparent\n");
-	else if ((uint8_t)*data == 0xAA)
-		seq_printf(m, "phy repeater mode: non-transparent\n");
-	else if ((uint8_t)*data == 0x00)
-		seq_printf(m, "phy repeater mode: non lttpr\n");
-	else
-		seq_printf(m, "phy repeater mode: read error\n");
-
-	kfree(data);
+	seq_puts(m, "\n");
 	return 0;
 }