drm/fsl-dcu: implement suspend/resume using atomic helpers

Use the drm_atomic_helper_suspend() and drm_atomic_helper_resume()
helpers to implement subsystem-level suspend/resume. This replaces
the (non-functional) regmap cache based suspend resume functionality.
Signed-off-by: Stefan Agner <stefan@agner.ch>

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c

@@ -11,6 +11,7 @@
 
 #include <linux/clk.h>
 #include <linux/clk-provider.h>
+#include <linux/console.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
 #include <linux/mm.h>
@@ -22,6 +23,7 @@
 #include <linux/regmap.h>
 
 #include <drm/drmP.h>
+#include <drm/drm_atomic_helper.h>
 #include <drm/drm_crtc_helper.h>
 #include <drm/drm_fb_cma_helper.h>
 #include <drm/drm_gem_cma_helper.h>
@@ -42,10 +44,8 @@ static const struct regmap_config fsl_dcu_regmap_config = {
 	.reg_bits = 32,
 	.reg_stride = 4,
 	.val_bits = 32,
-	.cache_type = REGCACHE_FLAT,
 
 	.volatile_reg = fsl_dcu_drm_is_volatile_reg,
-	.max_register = 0x11fc,
 };
 
 static int fsl_dcu_drm_irq_init(struct drm_device *dev)
@@ -229,9 +229,25 @@ static int fsl_dcu_drm_pm_suspend(struct device *dev)
 	if (!fsl_dev)
 		return 0;
 
+	disable_irq(fsl_dev->irq);
 	drm_kms_helper_poll_disable(fsl_dev->drm);
-	regcache_cache_only(fsl_dev->regmap, true);
-	regcache_mark_dirty(fsl_dev->regmap);
+
+	console_lock();
+	drm_fbdev_cma_set_suspend(fsl_dev->fbdev, 1);
+	console_unlock();
+
+	fsl_dev->state = drm_atomic_helper_suspend(fsl_dev->drm);
+	if (IS_ERR(fsl_dev->state)) {
+		console_lock();
+		drm_fbdev_cma_set_suspend(fsl_dev->fbdev, 0);
+		console_unlock();
+
+		drm_kms_helper_poll_enable(fsl_dev->drm);
+		enable_irq(fsl_dev->irq);
+		return PTR_ERR(fsl_dev->state);
+	}
+
+	clk_disable_unprepare(fsl_dev->pix_clk);
 	clk_disable_unprepare(fsl_dev->clk);
 
 	return 0;
@@ -251,9 +267,21 @@ static int fsl_dcu_drm_pm_resume(struct device *dev)
 		return ret;
 	}
 
+	ret = clk_prepare_enable(fsl_dev->pix_clk);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable pix clk\n");
+		return ret;
+	}
+
+	fsl_dcu_drm_init_planes(fsl_dev->drm);
+	drm_atomic_helper_resume(fsl_dev->drm, fsl_dev->state);
+
+	console_lock();
+	drm_fbdev_cma_set_suspend(fsl_dev->fbdev, 0);
+	console_unlock();
+
 	drm_kms_helper_poll_enable(fsl_dev->drm);
-	regcache_cache_only(fsl_dev->regmap, false);
-	regcache_sync(fsl_dev->regmap);
+	enable_irq(fsl_dev->irq);
 
 	return 0;
 }

drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.h

@@ -194,6 +194,7 @@ struct fsl_dcu_drm_device {
 	struct drm_encoder encoder;
 	struct fsl_dcu_drm_connector connector;
 	const struct fsl_dcu_soc_data *soc;
+	struct drm_atomic_state *state;
 };
 
 void fsl_dcu_fbdev_init(struct drm_device *dev);