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Subject[PATCH v2 1/3] mailbox: sprd: Introduce refcnt when clients requests/free channels
Date
From: Orson Zhai <orson.zhai@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. And fix the crash problem when early
interrupts come from channel which has not been requested by client yet.

Fixes: ca27fc26cd22 ("mailbox: sprd: Add Spreadtrum mailbox driver")
Signed-off-by: Orson Zhai <orson.zhai@unisoc.com>
---
drivers/mailbox/sprd-mailbox.c | 43 +++++++++++++++++++++++-----------
1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/drivers/mailbox/sprd-mailbox.c b/drivers/mailbox/sprd-mailbox.c
index f6fab24ae8a9..920de7b9dce1 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];
};

@@ -115,7 +117,11 @@ static irqreturn_t sprd_mbox_outbox_isr(int irq, void *data)
id = readl(priv->outbox_base + SPRD_MBOX_ID);

chan = &priv->chan[id];
- mbox_chan_received_data(chan, (void *)msg);
+ if (chan->cl)
+ mbox_chan_received_data(chan, (void *)msg);
+ else
+ dev_warn_ratelimited(priv->dev,
+ "message's been dropped at ch[%d]\n", id);

/* Trigger to update outbox FIFO pointer */
writel(0x1, priv->outbox_base + SPRD_MBOX_TRIGGER);
@@ -215,18 +221,22 @@ 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 +245,13 @@ 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 +280,7 @@ static int sprd_mbox_probe(struct platform_device *pdev)
return -ENOMEM;

priv->dev = dev;
+ mutex_init(&priv->lock);

/*
* The Spreadtrum mailbox uses an inbox to send messages to the target
--
2.17.1
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