drm/stm: support runtime power management

This patch enables runtime power management (runtime PM) support for
the display controller. pm_runtime_enable() and pm_runtime_disable()
are added during ltdc load and unload respectively.
pm_runtime_get_sync() and pm_runtime_put_sync() are added for ltdc
register access.

Signed-off-by: Yannick Fertré <yannick.fertre@st.com>
Acked-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1559550722-14091-1-git-send-email-yannick.fertre@st.com

drivers/gpu/drm/stm/drv.c

@@ -12,6 +12,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <linux/of_platform.h>
+#include <linux/pm_runtime.h>
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
@@ -135,14 +136,15 @@ static __maybe_unused int drv_suspend(struct device *dev)
 	struct ltdc_device *ldev = ddev->dev_private;
 	struct drm_atomic_state *state;
 
-	drm_kms_helper_poll_disable(ddev);
+	if (WARN_ON(!ldev->suspend_state))
+		return -ENOENT;
+
 	state = drm_atomic_helper_suspend(ddev);
-	if (IS_ERR(state)) {
-		drm_kms_helper_poll_enable(ddev);
+	if (IS_ERR(state))
 		return PTR_ERR(state);
-	}
+
 	ldev->suspend_state = state;
-	ltdc_suspend(ddev);
+	pm_runtime_force_suspend(dev);
 
 	return 0;
 }
@@ -151,16 +153,41 @@ static __maybe_unused int drv_resume(struct device *dev)
 {
 	struct drm_device *ddev = dev_get_drvdata(dev);
 	struct ltdc_device *ldev = ddev->dev_private;
+	int ret;
 
-	ltdc_resume(ddev);
-	drm_atomic_helper_resume(ddev, ldev->suspend_state);
-	drm_kms_helper_poll_enable(ddev);
+	pm_runtime_force_resume(dev);
+	ret = drm_atomic_helper_resume(ddev, ldev->suspend_state);
+	if (ret) {
+		pm_runtime_force_suspend(dev);
+		ldev->suspend_state = NULL;
+		return ret;
+	}
 
 	return 0;
 }
 
+static __maybe_unused int drv_runtime_suspend(struct device *dev)
+{
+	struct drm_device *ddev = dev_get_drvdata(dev);
+
+	DRM_DEBUG_DRIVER("\n");
+	ltdc_suspend(ddev);
+
+	return 0;
+}
+
+static __maybe_unused int drv_runtime_resume(struct device *dev)
+{
+	struct drm_device *ddev = dev_get_drvdata(dev);
+
+	DRM_DEBUG_DRIVER("\n");
+	return ltdc_resume(ddev);
+}
+
 static const struct dev_pm_ops drv_pm_ops = {
 	SET_SYSTEM_SLEEP_PM_OPS(drv_suspend, drv_resume)
+	SET_RUNTIME_PM_OPS(drv_runtime_suspend,
+			   drv_runtime_resume, NULL)
 };
 
 static int stm_drm_platform_probe(struct platform_device *pdev)

drivers/gpu/drm/stm/ltdc.c

@@ -16,6 +16,7 @@
 #include <linux/of_address.h>
 #include <linux/of_graph.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/reset.h>
 
 #include <drm/drm_atomic.h>
@@ -444,6 +445,7 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
 				     struct drm_crtc_state *old_state)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct drm_device *ddev = crtc->dev;
 
 	DRM_DEBUG_DRIVER("\n");
 
@@ -457,6 +459,8 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
 
 	/* immediately commit disable of layers before switching off LTDC */
 	reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR);
+
+	pm_runtime_put_sync(ddev->dev);
 }
 
 #define CLK_TOLERANCE_HZ 50
@@ -505,17 +509,31 @@ static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc,
 				 struct drm_display_mode *adjusted_mode)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct drm_device *ddev = crtc->dev;
 	int rate = mode->clock * 1000;
+	bool runtime_active;
+	int ret;
+
+	runtime_active = pm_runtime_active(ddev->dev);
+
+	if (runtime_active)
+		pm_runtime_put_sync(ddev->dev);
 
-	clk_disable(ldev->pixel_clk);
 	if (clk_set_rate(ldev->pixel_clk, rate) < 0) {
 		DRM_ERROR("Cannot set rate (%dHz) for pixel clk\n", rate);
 		return false;
 	}
-	clk_enable(ldev->pixel_clk);
 
 	adjusted_mode->clock = clk_get_rate(ldev->pixel_clk) / 1000;
 
+	if (runtime_active) {
+		ret = pm_runtime_get_sync(ddev->dev);
+		if (ret) {
+			DRM_ERROR("Failed to fixup mode, cannot get sync\n");
+			return false;
+		}
+	}
+
 	DRM_DEBUG_DRIVER("requested clock %dkHz, adjusted clock %dkHz\n",
 			 mode->clock, adjusted_mode->clock);
 
@@ -525,11 +543,21 @@ static bool ltdc_crtc_mode_fixup(struct drm_crtc *crtc,
 static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct drm_device *ddev = crtc->dev;
 	struct drm_display_mode *mode = &crtc->state->adjusted_mode;
 	struct videomode vm;
 	u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
 	u32 total_width, total_height;
 	u32 val;
+	int ret;
+
+	if (!pm_runtime_active(ddev->dev)) {
+		ret = pm_runtime_get_sync(ddev->dev);
+		if (ret) {
+			DRM_ERROR("Failed to set mode, cannot get sync\n");
+			return;
+		}
+	}
 
 	drm_display_mode_to_videomode(mode, &vm);
 
@@ -590,6 +618,7 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc,
 				   struct drm_crtc_state *old_crtc_state)
 {
 	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
+	struct drm_device *ddev = crtc->dev;
 	struct drm_pending_vblank_event *event = crtc->state->event;
 
 	DRM_DEBUG_ATOMIC("\n");
@@ -602,12 +631,12 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc,
 	if (event) {
 		crtc->state->event = NULL;
 
-		spin_lock_irq(&crtc->dev->event_lock);
+		spin_lock_irq(&ddev->event_lock);
 		if (drm_crtc_vblank_get(crtc) == 0)
 			drm_crtc_arm_vblank_event(crtc, event);
 		else
 			drm_crtc_send_vblank_event(crtc, event);
-		spin_unlock_irq(&crtc->dev->event_lock);
+		spin_unlock_irq(&ddev->event_lock);
 	}
 }
 
@@ -663,6 +692,7 @@ bool ltdc_crtc_scanoutpos(struct drm_device *ddev, unsigned int pipe,
 	 * Computation for the two first cases are identical so we can
 	 * simplify the code and only test if line > vactive_end
 	 */
+	if (pm_runtime_active(ddev->dev)) {
 		line = reg_read(ldev->regs, LTDC_CPSR) & CPSR_CYPOS;
 		vactive_start = reg_read(ldev->regs, LTDC_BPCR) & BPCR_AVBP;
 		vactive_end = reg_read(ldev->regs, LTDC_AWCR) & AWCR_AAH;
@@ -672,6 +702,9 @@ bool ltdc_crtc_scanoutpos(struct drm_device *ddev, unsigned int pipe,
 			*vpos = line - vtotal - vactive_start;
 		else
 			*vpos = line - vactive_start;
+	} else {
+		*vpos = 0;
+	}
 
 	*hpos = 0;
 
@@ -1243,8 +1276,11 @@ int ltdc_load(struct drm_device *ddev)
 	/* Allow usage of vblank without having to call drm_irq_install */
 	ddev->irq_enabled = 1;
 
-	return 0;
+	clk_disable_unprepare(ldev->pixel_clk);
 
+	pm_runtime_enable(ddev->dev);
+
+	return 0;
 err:
 	for (i = 0; i < MAX_ENDPOINTS; i++)
 		drm_panel_bridge_remove(bridge[i]);
@@ -1256,7 +1292,6 @@ int ltdc_load(struct drm_device *ddev)
 
 void ltdc_unload(struct drm_device *ddev)
 {
-	struct ltdc_device *ldev = ddev->dev_private;
 	int i;
 
 	DRM_DEBUG_DRIVER("\n");
@@ -1264,7 +1299,7 @@ void ltdc_unload(struct drm_device *ddev)
 	for (i = 0; i < MAX_ENDPOINTS; i++)
 		drm_of_panel_bridge_remove(ddev->dev->of_node, 0, i);
 
-	clk_disable_unprepare(ldev->pixel_clk);
+	pm_runtime_disable(ddev->dev);
 }
 
 MODULE_AUTHOR("Philippe Cornu <philippe.cornu@st.com>");