drm/rockchip: psr: Avoid redundant calls to .set() callback

The first time after we call rockchip_drm_do_flush() after
rockchip_drm_psr_register(), we go from PSR_DISABLE to PSR_FLUSH. The
difference between PSR_DISABLE and PSR_FLUSH is whether or not we have a
delayed work pending - PSR is off in either state.  However
psr_set_state() only catches the transition from PSR_FLUSH to
PSR_DISABLE (which never happens), while going from PSR_DISABLE to
PSR_FLUSH triggers a call to psr->set() to disable PSR while it's
already disabled. This triggers the eDP PHY power-on sequence without
being shut down first and this seems to occasionally leave the encoder
unable to later enable PSR. Let's just simplify the state machine and
simply consider PSR_DISABLE and PSR_FLUSH the same state.

Signed-off-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Kristian H. Kristensen <hoegsberg@chromium.org>
Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180423105003.9004-25-enric.balletbo@collabora.com

drivers/gpu/drm/rockchip/rockchip_drm_psr.c

@@ -20,19 +20,13 @@
 
 #define PSR_FLUSH_TIMEOUT_MS	100
 
-enum psr_state {
-	PSR_FLUSH,
-	PSR_ENABLE,
-	PSR_DISABLE,
-};
-
 struct psr_drv {
 	struct list_head	list;
 	struct drm_encoder	*encoder;
 
 	struct mutex		lock;
 	bool			active;
-	enum psr_state		state;
+	bool			enabled;
 
 	struct delayed_work	flush_work;
 
@@ -73,52 +67,22 @@ static struct psr_drv *find_psr_by_encoder(struct drm_encoder *encoder)
 	return psr;
 }
 
-static void psr_set_state_locked(struct psr_drv *psr, enum psr_state state)
+static int psr_set_state_locked(struct psr_drv *psr, bool enable)
 {
-	/*
-	 * Allowed finite state machine:
-	 *
-	 *   PSR_ENABLE  < = = = = = >  PSR_FLUSH
-	 *       | ^                        |
-	 *       | |                        |
-	 *       v |                        |
-	 *   PSR_DISABLE < - - - - - - - - -
-	 */
-	if (state == psr->state || !psr->active)
-		return;
+	int ret;
 
-	/* Already disabled in flush, change the state, but not the hardware */
-	if (state == PSR_DISABLE && psr->state == PSR_FLUSH) {
-		psr->state = state;
-		return;
-	}
+	if (!psr->active)
+		return -EINVAL;
 
-	/* Actually commit the state change to hardware */
-	switch (state) {
-	case PSR_ENABLE:
-		if (psr->set(psr->encoder, true))
-			return;
-		break;
+	if (enable == psr->enabled)
+		return 0;
 
-	case PSR_DISABLE:
-	case PSR_FLUSH:
-		if (psr->set(psr->encoder, false))
-			return;
-		break;
+	ret = psr->set(psr->encoder, enable);
+	if (ret)
+		return ret;
 
-	default:
-		pr_err("%s: Unknown state %d\n", __func__, state);
-		return;
-	}
-
-	psr->state = state;
-}
-
-static void psr_set_state(struct psr_drv *psr, enum psr_state state)
-{
-	mutex_lock(&psr->lock);
-	psr_set_state_locked(psr, state);
-	mutex_unlock(&psr->lock);
+	psr->enabled = enable;
+	return 0;
 }
 
 static void psr_flush_handler(struct work_struct *work)
@@ -126,10 +90,8 @@ static void psr_flush_handler(struct work_struct *work)
 	struct psr_drv *psr = container_of(to_delayed_work(work),
 					   struct psr_drv, flush_work);
 
-	/* If the state has changed since we initiated the flush, do nothing */
 	mutex_lock(&psr->lock);
-	if (psr->state == PSR_FLUSH)
-		psr_set_state_locked(psr, PSR_ENABLE);
+	psr_set_state_locked(psr, true);
 	mutex_unlock(&psr->lock);
 }
 
@@ -171,6 +133,7 @@ int rockchip_drm_psr_deactivate(struct drm_encoder *encoder)
 
 	mutex_lock(&psr->lock);
 	psr->active = false;
+	psr->enabled = false;
 	mutex_unlock(&psr->lock);
 	cancel_delayed_work_sync(&psr->flush_work);
 
@@ -180,8 +143,13 @@ EXPORT_SYMBOL(rockchip_drm_psr_deactivate);
 
 static void rockchip_drm_do_flush(struct psr_drv *psr)
 {
-	psr_set_state(psr, PSR_FLUSH);
-	mod_delayed_work(system_wq, &psr->flush_work, PSR_FLUSH_TIMEOUT_MS);
+	cancel_delayed_work_sync(&psr->flush_work);
+
+	mutex_lock(&psr->lock);
+	if (!psr_set_state_locked(psr, false))
+		mod_delayed_work(system_wq, &psr->flush_work,
+				 PSR_FLUSH_TIMEOUT_MS);
+	mutex_unlock(&psr->lock);
 }
 
 /**
@@ -250,8 +218,8 @@ int rockchip_drm_psr_register(struct drm_encoder *encoder,
 	INIT_DELAYED_WORK(&psr->flush_work, psr_flush_handler);
 	mutex_init(&psr->lock);
 
-	psr->active = true;
-	psr->state = PSR_DISABLE;
+	psr->active = false;
+	psr->enabled = false;
 	psr->encoder = encoder;
 	psr->set = psr_set;