drm/amd/display: Don't try to enable/disable HPD when unavailable

VGA connectors don't have HPD (hotplug detection), so don't
touch any HPD related registers for VGA.

Determine whether hotplug detection is available by checking that
the interrupt source is invalid.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

Author: Timur Kristóf

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

@@ -759,6 +759,7 @@ static ssize_t dp_phy_test_pattern_debugfs_write(struct file *f, const char __us
 	int max_param_num = 11;
 	enum dp_test_pattern test_pattern = DP_TEST_PATTERN_UNSUPPORTED;
 	bool disable_hpd = false;
+	bool supports_hpd = link->irq_source_hpd != DC_IRQ_SOURCE_INVALID;
 	bool valid_test_pattern = false;
 	uint8_t param_nums = 0;
 	/* init with default 80bit custom pattern */
@@ -850,7 +851,7 @@ static ssize_t dp_phy_test_pattern_debugfs_write(struct file *f, const char __us
 	 * because it might have been disabled after a test pattern was set.
 	 * AUX depends on HPD * sequence dependent, do not move!
 	 */
-	if (!disable_hpd)
+	if (supports_hpd && !disable_hpd)
 		dc_link_enable_hpd(link);
 
 	prefer_link_settings.lane_count = link->verified_link_cap.lane_count;
@@ -888,7 +889,7 @@ static ssize_t dp_phy_test_pattern_debugfs_write(struct file *f, const char __us
 	 * Need disable interrupt to avoid SW driver disable DP output. This is
 	 * done after the test pattern is set.
 	 */
-	if (valid_test_pattern && disable_hpd)
+	if (valid_test_pattern && supports_hpd && disable_hpd)
 		dc_link_disable_hpd(link);
 
 	kfree(wr_buf);