drm/amd/pm: Restore config space after reset

During mode-2 reset, pci config space registers are affected at device
side. However, certain platforms have switches which assign virtual BAR
addresses and returns the same even after device is reset. This
affects pci_restore_state() as it doesn't issue another config write, if
the value read is same as the saved value.

Add a workaround to write saved config space values from driver side.
Presently, these switches are in platforms with SMU v13.0.6 SOCs, hence
restrict the workaround only to those.
Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Asad Kamal <asad.kamal@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/pm/swsmu/smu13/smu_v13_0_6_ppt.c

@@ -2314,6 +2314,17 @@ static ssize_t smu_v13_0_6_get_gpu_metrics(struct smu_context *smu, void **table
 	return sizeof(*gpu_metrics);
 }
 
+static void smu_v13_0_6_restore_pci_config(struct smu_context *smu)
+{
+	struct amdgpu_device *adev = smu->adev;
+	int i;
+
+	for (i = 0; i < 16; i++)
+		pci_write_config_dword(adev->pdev, i * 4,
+				       adev->pdev->saved_config_space[i]);
+	pci_restore_msi_state(adev->pdev);
+}
+
 static int smu_v13_0_6_mode2_reset(struct smu_context *smu)
 {
 	int ret = 0, index;
@@ -2335,6 +2346,20 @@ static int smu_v13_0_6_mode2_reset(struct smu_context *smu)
 	/* Restore the config space saved during init */
 	amdgpu_device_load_pci_state(adev->pdev);
 
+	/* Certain platforms have switches which assign virtual BAR values to
+	 * devices. OS uses the virtual BAR values and device behind the switch
+	 * is assgined another BAR value. When device's config space registers
+	 * are queried, switch returns the virtual BAR values. When mode-2 reset
+	 * is performed, switch is unaware of it, and will continue to return
+	 * the same virtual values to the OS.This affects
+	 * pci_restore_config_space() API as it doesn't write the value saved if
+	 * the current value read from config space is the same as what is
+	 * saved. As a workaround, make sure the config space is restored
+	 * always.
+	 */
+	if (!(adev->flags & AMD_IS_APU))
+		smu_v13_0_6_restore_pci_config(smu);
+
 	dev_dbg(smu->adev->dev, "wait for reset ack\n");
 	do {
 		ret = smu_cmn_wait_for_response(smu);