drm/nouveau/tegra: Set clock rate if not set

If the GPU clock has not had a rate set, initialize it to the maximum
clock rate to make sure it does run.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

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

@@ -279,6 +279,7 @@ nvkm_device_tegra_new(const struct nvkm_device_tegra_func *func,
 		      struct nvkm_device **pdevice)
 {
 	struct nvkm_device_tegra *tdev;
+	unsigned long rate;
 	int ret;
 
 	if (!(tdev = kzalloc(sizeof(*tdev), GFP_KERNEL)))
@@ -307,6 +308,17 @@ nvkm_device_tegra_new(const struct nvkm_device_tegra_func *func,
 		goto free;
 	}
 
+	rate = clk_get_rate(tdev->clk);
+	if (rate == 0) {
+		ret = clk_set_rate(tdev->clk, ULONG_MAX);
+		if (ret < 0)
+			goto free;
+
+		rate = clk_get_rate(tdev->clk);
+
+		dev_dbg(&pdev->dev, "GPU clock set to %lu\n", rate);
+	}
+
 	if (func->require_ref_clk)
 		tdev->clk_ref = devm_clk_get(&pdev->dev, "ref");
 	if (IS_ERR(tdev->clk_ref)) {