drm/nouveau/platform: make VDD regulator optional

GP10B's power is managed by generic PM domains, so it does not require a
VDD regulator. Add this option into the chip function structure.
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/include/nvkm/core/tegra.h

@@ -42,6 +42,10 @@ struct nvkm_device_tegra_func {
 	 * Whether the chip requires a reference clock
 	 */
 	bool require_ref_clk;
+	/*
+	 * Whether the chip requires the VDD regulator
+	 */
+	bool require_vdd;
 };
 
 int nvkm_device_tegra_new(const struct nvkm_device_tegra_func *,

drivers/gpu/drm/nouveau/nouveau_platform.c

@@ -53,10 +53,12 @@ static int nouveau_platform_remove(struct platform_device *pdev)
 #if IS_ENABLED(CONFIG_OF)
 static const struct nvkm_device_tegra_func gk20a_platform_data = {
 	.iommu_bit = 34,
+	.require_vdd = true,
 };
 
 static const struct nvkm_device_tegra_func gm20b_platform_data = {
 	.iommu_bit = 34,
+	.require_vdd = true,
 	.require_ref_clk = true,
 };
 

drivers/gpu/drm/nouveau/nvkm/engine/device/tegra.c

@@ -28,9 +28,11 @@ nvkm_device_tegra_power_up(struct nvkm_device_tegra *tdev)
 {
 	int ret;
 
+	if (tdev->vdd) {
 		ret = regulator_enable(tdev->vdd);
 		if (ret)
 			goto err_power;
+	}
 
 	ret = clk_prepare_enable(tdev->clk);
 	if (ret)
@@ -67,6 +69,7 @@ nvkm_device_tegra_power_up(struct nvkm_device_tegra *tdev)
 err_clk_ref:
 	clk_disable_unprepare(tdev->clk);
 err_clk:
+	if (tdev->vdd)
 		regulator_disable(tdev->vdd);
 err_power:
 	return ret;
@@ -75,6 +78,8 @@ nvkm_device_tegra_power_up(struct nvkm_device_tegra *tdev)
 static int
 nvkm_device_tegra_power_down(struct nvkm_device_tegra *tdev)
 {
+	int ret;
+
 	reset_control_assert(tdev->rst);
 	udelay(10);
 
@@ -84,7 +89,13 @@ nvkm_device_tegra_power_down(struct nvkm_device_tegra *tdev)
 	clk_disable_unprepare(tdev->clk);
 	udelay(10);
 
-	return regulator_disable(tdev->vdd);
+	if (tdev->vdd) {
+		ret = regulator_disable(tdev->vdd);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
 }
 
 static void
@@ -264,11 +275,13 @@ nvkm_device_tegra_new(const struct nvkm_device_tegra_func *func,
 	tdev->func = func;
 	tdev->pdev = pdev;
 
+	if (func->require_vdd) {
 		tdev->vdd = devm_regulator_get(&pdev->dev, "vdd");
 		if (IS_ERR(tdev->vdd)) {
 			ret = PTR_ERR(tdev->vdd);
 			goto free;
 		}
+	}
 
 	tdev->rst = devm_reset_control_get(&pdev->dev, "gpu");
 	if (IS_ERR(tdev->rst)) {