drm/ingenic: ipu: Only enable clock when needed

Instead of keeping the IPU clock enabled constantly, enable and disable
it on demand, when the IPU plane is used. That way, we won't use any
extra power when the IPU is not used.

v2: Explain the reason of this patch
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200730144830.10479-4-paul@crapouillou.net

drivers/gpu/drm/ingenic/ingenic-ipu.c

@@ -49,6 +49,7 @@ struct ingenic_ipu {
 	struct regmap *map;
 	struct clk *clk;
 	const struct soc_info *soc_info;
+	bool clk_enabled;
 
 	unsigned int num_w, num_h, denom_w, denom_h;
 
@@ -288,12 +289,23 @@ static void ingenic_ipu_plane_atomic_update(struct drm_plane *plane,
 	const struct drm_format_info *finfo;
 	u32 ctrl, stride = 0, coef_index = 0, format = 0;
 	bool needs_modeset, upscaling_w, upscaling_h;
+	int err;
 
 	if (!state || !state->fb)
 		return;
 
 	finfo = drm_format_info(state->fb->format->format);
 
+	if (!ipu->clk_enabled) {
+		err = clk_enable(ipu->clk);
+		if (err) {
+			dev_err(ipu->dev, "Unable to enable clock: %d\n", err);
+			return;
+		}
+
+		ipu->clk_enabled = true;
+	}
+
 	/* Reset all the registers if needed */
 	needs_modeset = drm_atomic_crtc_needs_modeset(state->crtc->state);
 	if (needs_modeset) {
@@ -578,6 +590,11 @@ static void ingenic_ipu_plane_atomic_disable(struct drm_plane *plane,
 	regmap_clear_bits(ipu->map, JZ_REG_IPU_CTRL, JZ_IPU_CTRL_CHIP_EN);
 
 	ingenic_drm_plane_disable(ipu->master, plane);
+
+	if (ipu->clk_enabled) {
+		clk_disable(ipu->clk);
+		ipu->clk_enabled = false;
+	}
 }
 
 static const struct drm_plane_helper_funcs ingenic_ipu_plane_helper_funcs = {
@@ -761,9 +778,9 @@ static int ingenic_ipu_bind(struct device *dev, struct device *master, void *d)
 	drm_object_attach_property(&plane->base, ipu->sharpness_prop,
 				   ipu->sharpness);
 
-	err = clk_prepare_enable(ipu->clk);
+	err = clk_prepare(ipu->clk);
 	if (err) {
-		dev_err(dev, "Unable to enable clock\n");
+		dev_err(dev, "Unable to prepare clock\n");
 		return err;
 	}
 
@@ -775,7 +792,7 @@ static void ingenic_ipu_unbind(struct device *dev,
 {
 	struct ingenic_ipu *ipu = dev_get_drvdata(dev);
 
-	clk_disable_unprepare(ipu->clk);
+	clk_unprepare(ipu->clk);
 }
 
 static const struct component_ops ingenic_ipu_ops = {