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Mon, 08 Feb 2021 19:28:43 -0800 (PST) Date: Tue, 9 Feb 2021 11:28:38 +0800 From: Orson Zhai To: Baolin Wang Cc: Rob Herring , Jassi Brar , Chunyan Zhang , Mark Brown , Devicetree List , LKML , Haidong Yao , Orson Zhai Subject: Re: [PATCH 1/3] mailbox: sprd: Introduce refcnt when clients requests/free channels Message-ID: <20210209032838.GA24248@lenovo> Mail-Followup-To: Baolin Wang , Rob Herring , Jassi Brar , Chunyan Zhang , Mark Brown , Devicetree List , LKML , Haidong Yao , Orson Zhai References: <1612785064-3072-1-git-send-email-orsonzhai@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Mon, Feb 08, 2021 at 10:06:47PM +0800, Baolin Wang wrote: > Hi Orson, > > On Mon, Feb 8, 2021 at 7:52 PM Orson Zhai wrote: > > > > From: Orson Zhai > > > > 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 > > --- > > 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. Yes, atomic could make refcnt itself safe. But mutex lock is to make whole processing of reading/writing registers safe. Consider case like this: channel #1 channel #2 ------------------------------------- startup ..... shutdown startup |-refcnt==0 | | |-retcnt+1 | |-enable mailbox |-disable mailbox Mailbox will be wrongly disabled after client requests channel #2's startup. > > > > > 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. Right, will remove at next version. Thanks for reviewing! -Orson > > > + mutex_init(&priv->lock); > > > > /* > > * The Spreadtrum mailbox uses an inbox to send messages to the target > > -- > > 2.7.4 > > > > > -- > Baolin Wang