[PATCH 1/3] mailbox: sprd: Introduce refcnt when clients requests/free channels

[Orson Zhai]

From: Orson Zhai <orson.z...@unisoc.com>

Unisoc mailbox has no way to be enabled/disabled for any single channel.
They can only be set to startup or shutdown as a whole device at same time.

Add a variable to count references to avoid mailbox FIFO being reset
unexpectedly when clients are requesting or freeing channels.

Also add a lock to dismiss possible conflicts from register r/w in
different startup or shutdown threads.

Fixes: ca27fc26cd22 ("mailbox: sprd: Add Spreadtrum mailbox driver")
Signed-off-by: Orson Zhai <orson.z...@unisoc.com>
---
 drivers/mailbox/sprd-mailbox.c | 38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/drivers/mailbox/sprd-mailbox.c b/drivers/mailbox/sprd-mailbox.c
index f6fab24..e606f52 100644
--- a/drivers/mailbox/sprd-mailbox.c
+++ b/drivers/mailbox/sprd-mailbox.c
@@ -60,6 +60,8 @@ struct sprd_mbox_priv {
        struct clk              *clk;
        u32                     outbox_fifo_depth;
 
+       struct mutex            lock;
+       u32                     refcnt;
        struct mbox_chan        chan[SPRD_MBOX_CHAN_MAX];
 };
 
@@ -215,18 +217,22 @@ static int sprd_mbox_startup(struct mbox_chan *chan)
        struct sprd_mbox_priv *priv = to_sprd_mbox_priv(chan->mbox);
        u32 val;
 
-       /* Select outbox FIFO mode and reset the outbox FIFO status */
-       writel(0x0, priv->outbox_base + SPRD_MBOX_FIFO_RST);
+       mutex_lock(&priv->lock);
+       if (priv->refcnt++ == 0) {
+               /* Select outbox FIFO mode and reset the outbox FIFO status */
+               writel(0x0, priv->outbox_base + SPRD_MBOX_FIFO_RST);
 
-       /* Enable inbox FIFO overflow and delivery interrupt */
-       val = readl(priv->inbox_base + SPRD_MBOX_IRQ_MSK);
-       val &= ~(SPRD_INBOX_FIFO_OVERFLOW_IRQ | SPRD_INBOX_FIFO_DELIVER_IRQ);
-       writel(val, priv->inbox_base + SPRD_MBOX_IRQ_MSK);
+               /* Enable inbox FIFO overflow and delivery interrupt */
+               val = readl(priv->inbox_base + SPRD_MBOX_IRQ_MSK);
+               val &= ~(SPRD_INBOX_FIFO_OVERFLOW_IRQ | 
SPRD_INBOX_FIFO_DELIVER_IRQ);
+               writel(val, priv->inbox_base + SPRD_MBOX_IRQ_MSK);
 
-       /* Enable outbox FIFO not empty interrupt */
-       val = readl(priv->outbox_base + SPRD_MBOX_IRQ_MSK);
-       val &= ~SPRD_OUTBOX_FIFO_NOT_EMPTY_IRQ;
-       writel(val, priv->outbox_base + SPRD_MBOX_IRQ_MSK);
+               /* Enable outbox FIFO not empty interrupt */
+               val = readl(priv->outbox_base + SPRD_MBOX_IRQ_MSK);
+               val &= ~SPRD_OUTBOX_FIFO_NOT_EMPTY_IRQ;
+               writel(val, priv->outbox_base + SPRD_MBOX_IRQ_MSK);
+       }
+       mutex_unlock(&priv->lock);
 
        return 0;
 }
@@ -235,9 +241,13 @@ static void sprd_mbox_shutdown(struct mbox_chan *chan)
 {
        struct sprd_mbox_priv *priv = to_sprd_mbox_priv(chan->mbox);
 
-       /* Disable inbox & outbox interrupt */
-       writel(SPRD_INBOX_FIFO_IRQ_MASK, priv->inbox_base + SPRD_MBOX_IRQ_MSK);
-       writel(SPRD_OUTBOX_FIFO_IRQ_MASK, priv->outbox_base + 
SPRD_MBOX_IRQ_MSK);
+       mutex_lock(&priv->lock);
+       if (--priv->refcnt == 0) {
+               /* Disable inbox & outbox interrupt */
+               writel(SPRD_INBOX_FIFO_IRQ_MASK, priv->inbox_base + 
SPRD_MBOX_IRQ_MSK);
+               writel(SPRD_OUTBOX_FIFO_IRQ_MASK, priv->outbox_base + 
SPRD_MBOX_IRQ_MSK);
+       }
+       mutex_unlock(&priv->lock);
 }
 
 static const struct mbox_chan_ops sprd_mbox_ops = {
@@ -266,6 +276,8 @@ static int sprd_mbox_probe(struct platform_device *pdev)
                return -ENOMEM;
 
        priv->dev = dev;
+       priv->refcnt = 0;
+       mutex_init(&priv->lock);
 
        /*
         * The Spreadtrum mailbox uses an inbox to send messages to the target
-- 
2.7.4