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

On Mon, Feb 8, 2021 at 7:52 PM Orson Zhai <orsonzhai@gmail.com> wrote:
>
> 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.
>
> Fixes: ca27fc26cd22 ("mailbox: sprd: Add Spreadtrum mailbox driver")
> Signed-off-by: Orson Zhai <orson.zhai@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);

I think using the atomic_add/sub_and_test() related APIs can remove
the mutex 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;

No need to do this, the priv structure is already cleared to 0.

> + mutex_init(&priv->lock);
>
> /*
> * The Spreadtrum mailbox uses an inbox to send messages to the target
> --
> 2.7.4
>


--
Baolin Wang

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