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    Subject[PATCH 5.10 336/530] mailbox: sprd: Introduce refcnt when clients requests/free channels
    Date
    From: Orson Zhai <orson.zhai@unisoc.com>

    [ Upstream commit 9468ab84032f96496e998cfa173cd1d0ac316bcd ]

    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>
    Reviewed-by: Baolin Wang <baolin.wang7@gmail.com>
    Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 4c325301a2fe..94d9067dc8d0 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
    --
    2.30.2


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