[PATCH v2 3/6] drm/rockchip: Use a spinlock to protect psr state

[Sean Paul]

The handling of psr state is racey, shore that up with
a per-psr driver lock.

Signed-off-by: Sean Paul <seanpaul at chromium.org>
---

Changes in v2:
        - Rebased on 
https://cgit.freedesktop.org/~seanpaul/dogwood/log/?h=for-next

 drivers/gpu/drm/rockchip/rockchip_drm_psr.c | 26 +++++++++++++++++---------
 1 file changed, 17 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c 
b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
index 4c645d7..5bd54f2 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
@@ -30,6 +30,7 @@ struct psr_drv {
        struct list_head        list;
        struct drm_encoder      *encoder;

+       spinlock_t              lock;
        enum psr_state          state;

        struct timer_list       flush_timer;
@@ -55,7 +56,7 @@ out:
        return psr;
 }

-static void psr_set_state(struct psr_drv *psr, enum psr_state state)
+static void psr_set_state_locked(struct psr_drv *psr, enum psr_state state)
 {
        /*
         * Allowed finite state machine:
@@ -75,7 +76,6 @@ static void psr_set_state(struct psr_drv *psr, enum psr_state 
state)
        if (state == PSR_FLUSH && psr->state == PSR_DISABLE)
                return;

-       /* Only wrote in this work, no need lock protection */
        psr->state = state;

        /* Allow but no need hardware change, just need assign the state */
@@ -95,18 +95,28 @@ static void psr_set_state(struct psr_drv *psr, enum 
psr_state state)
        }
 }

+static void psr_set_state(struct psr_drv *psr, enum psr_state state)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&psr->lock, flags);
+       psr_set_state_locked(psr, state);
+       spin_unlock_irqrestore(&psr->lock, flags);
+}
+
 static void psr_flush_handler(unsigned long data)
 {
        struct psr_drv *psr = (struct psr_drv *)data;
+       unsigned long flags;

        if (!psr)
                return;

        /* State changed between flush time, then keep it */
-       if (psr->state != PSR_FLUSH)
-               return;
-
-       psr_set_state(psr, PSR_ENABLE);
+       spin_lock_irqsave(&psr->lock, flags);
+       if (psr->state == PSR_FLUSH)
+               psr_set_state_locked(psr, PSR_ENABLE);
+       spin_unlock_irqrestore(&psr->lock, flags);
 }

 /**
@@ -167,9 +177,6 @@ void rockchip_drm_psr_flush(struct drm_device *dev)

        spin_lock_irqsave(&drm_drv->psr_list_lock, flags);
        list_for_each_entry(psr, &drm_drv->psr_list, list) {
-               if (psr->state == PSR_DISABLE)
-                       continue;
-
                mod_timer(&psr->flush_timer,
                          round_jiffies_up(jiffies + PSR_FLUSH_TIMEOUT));

@@ -202,6 +209,7 @@ int rockchip_drm_psr_register(struct drm_encoder *encoder,
                return -ENOMEM;

        setup_timer(&psr->flush_timer, psr_flush_handler, (unsigned long)psr);
+       spin_lock_init(&psr->lock);

        psr->state = PSR_DISABLE;
        psr->encoder = encoder;
-- 
2.8.0.rc3.226.g39d4020