drm/amd/display: Ignore First MST Sideband Message Return Error

[why]
First MST sideband message returns AUX_RET_ERROR_HPD_DISCON
on certain intel platform. Aux transaction considered failure
if HPD unexpected pulled low. The actual aux transaction success
in such case, hence do not return error.

[how]
Not returning error when AUX_RET_ERROR_HPD_DISCON detected
on the first sideband message.

v2: squash in additional DMI entries
v3: squash in static fix

Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Acked-by: Solomon Chiu <solomon.chiu@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -72,6 +72,7 @@
 #include <linux/pci.h>
 #include <linux/firmware.h>
 #include <linux/component.h>
+#include <linux/dmi.h>
 
 #include <drm/display/drm_dp_mst_helper.h>
 #include <drm/display/drm_hdmi_helper.h>
@@ -1401,6 +1402,41 @@ static bool dm_should_disable_stutter(struct pci_dev *pdev)
 	return false;
 }
 
+static const struct dmi_system_id hpd_disconnect_quirk_table[] = {
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Precision 3660"),
+		},
+	},
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Precision 3260"),
+		},
+	},
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
+			DMI_MATCH(DMI_PRODUCT_NAME, "Precision 3460"),
+		},
+	},
+	{}
+};
+
+static void retrieve_dmi_info(struct amdgpu_display_manager *dm)
+{
+	const struct dmi_system_id *dmi_id;
+
+	dm->aux_hpd_discon_quirk = false;
+
+	dmi_id = dmi_first_match(hpd_disconnect_quirk_table);
+	if (dmi_id) {
+		dm->aux_hpd_discon_quirk = true;
+		DRM_INFO("aux_hpd_discon_quirk attached\n");
+	}
+}
+
 static int amdgpu_dm_init(struct amdgpu_device *adev)
 {
 	struct dc_init_data init_data;
@@ -1529,6 +1565,9 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
 	init_data.flags.enable_mipi_converter_optimization = true;
 
 	INIT_LIST_HEAD(&adev->dm.da_list);
+
+	retrieve_dmi_info(&adev->dm);
+
 	/* Display Core create. */
 	adev->dm.dc = dc_create(&init_data);
 

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h

@@ -547,6 +547,14 @@ struct amdgpu_display_manager {
 	 * last successfully applied backlight values.
 	 */
 	u32 actual_brightness[AMDGPU_DM_MAX_NUM_EDP];
+
+	/**
+	 * @aux_hpd_discon_quirk:
+	 *
+	 * quirk for hpd discon while aux is on-going.
+	 * occurred on certain intel platform
+	 */
+	bool aux_hpd_discon_quirk;
 };
 
 enum dsc_clock_force_state {

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

@@ -56,6 +56,8 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 	ssize_t result = 0;
 	struct aux_payload payload;
 	enum aux_return_code_type operation_result;
+	struct amdgpu_device *adev;
+	struct ddc_service *ddc;
 
 	if (WARN_ON(msg->size > 16))
 		return -E2BIG;
@@ -74,6 +76,21 @@ static ssize_t dm_dp_aux_transfer(struct drm_dp_aux *aux,
 	result = dc_link_aux_transfer_raw(TO_DM_AUX(aux)->ddc_service, &payload,
 				      &operation_result);
 
+	/*
+	 * w/a on certain intel platform where hpd is unexpected to pull low during
+	 * 1st sideband message transaction by return AUX_RET_ERROR_HPD_DISCON
+	 * aux transaction is succuess in such case, therefore bypass the error
+	 */
+	ddc = TO_DM_AUX(aux)->ddc_service;
+	adev = ddc->ctx->driver_context;
+	if (adev->dm.aux_hpd_discon_quirk) {
+		if (msg->address == DP_SIDEBAND_MSG_DOWN_REQ_BASE &&
+			operation_result == AUX_RET_ERROR_HPD_DISCON) {
+			result = 0;
+			operation_result = AUX_RET_SUCCESS;
+		}
+	}
+
 	if (payload.write && result >= 0)
 		result = msg->size;