[PATCH] rpmsg: glink: Use spinlock in tx path

[PATCH] rpmsg: glink: Use spinlock in tx path

[Bjorn Andersson]

Switch the tx_lock to a spinlock we allow clients to use rpmsg_trysend()
from atomic context.

In order to allow clients to sleep while waiting for space in the FIFO
we release the lock temporarily around the delay; which should be
replaced by sending a READ_NOTIF and waiting for the remote to signal
us that space has been made available.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
---
 drivers/rpmsg/qcom_glink_native.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index e0f31ed096a5..6e950e9afa82 100644
--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -113,7 +113,7 @@ struct qcom_glink {
 	spinlock_t rx_lock;
 	struct list_head rx_queue;
 
-	struct mutex tx_lock;
+	spinlock_t tx_lock;
 
 	spinlock_t idr_lock;
 	struct idr lcids;
@@ -288,15 +288,14 @@ static int qcom_glink_tx(struct qcom_glink *glink,
 			 const void *data, size_t dlen, bool wait)
 {
 	unsigned int tlen = hlen + dlen;
+	unsigned long flags;
 	int ret;
 
 	/* Reject packets that are too big */
 	if (tlen >= glink->tx_pipe->length)
 		return -EINVAL;
 
-	ret = mutex_lock_interruptible(&glink->tx_lock);
-	if (ret)
-		return ret;
+	spin_lock_irqsave(&glink->tx_lock, flags);
 
 	while (qcom_glink_tx_avail(glink) < tlen) {
 		if (!wait) {
@@ -304,7 +303,12 @@ static int qcom_glink_tx(struct qcom_glink *glink,
 			goto out;
 		}
 
+		/* Wait without holding the tx_lock */
+		spin_unlock_irqrestore(&glink->tx_lock, flags);
+
 		usleep_range(10000, 15000);
+
+		spin_lock_irqsave(&glink->tx_lock, flags);
 	}
 
 	qcom_glink_tx_write(glink, hdr, hlen, data, dlen);
@@ -313,7 +317,7 @@ static int qcom_glink_tx(struct qcom_glink *glink,
 	mbox_client_txdone(glink->mbox_chan, 0);
 
 out:
-	mutex_unlock(&glink->tx_lock);
+	spin_unlock_irqrestore(&glink->tx_lock, flags);
 
 	return ret;
 }
@@ -1567,7 +1571,7 @@ struct qcom_glink *qcom_glink_native_probe(struct device *dev,
 	glink->features = features;
 	glink->intentless = intentless;
 
-	mutex_init(&glink->tx_lock);
+	spin_lock_init(&glink->tx_lock);
 	spin_lock_init(&glink->rx_lock);
 	INIT_LIST_HEAD(&glink->rx_queue);
 	INIT_WORK(&glink->rx_work, qcom_glink_work);
-- 
2.15.0

Re: [PATCH] rpmsg: glink: Use spinlock in tx path

[Srinivas Kandagatla]

On 14/02/18 03:04, Bjorn Andersson wrote:
> Switch the tx_lock to a spinlock we allow clients to use rpmsg_trysend()
> from atomic context.
> 
> In order to allow clients to sleep while waiting for space in the FIFO
> we release the lock temporarily around the delay; which should be
> replaced by sending a READ_NOTIF and waiting for the remote to signal
> us that space has been made available.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
> ---

with ret set to 0 in qcom_glink_tx()

Tested-by: Srinivas kandagatla <srinivas.kandagatla@linaro.org>

>   drivers/rpmsg/qcom_glink_native.c | 16 ++++++++++------
>   1 file changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
> index e0f31ed096a5..6e950e9afa82 100644
> --- a/drivers/rpmsg/qcom_glink_native.c
> +++ b/drivers/rpmsg/qcom_glink_native.c
> @@ -113,7 +113,7 @@ struct qcom_glink {
>   	spinlock_t rx_lock;
>   	struct list_head rx_queue;
>   
> -	struct mutex tx_lock;
> +	spinlock_t tx_lock;
>   
>   	spinlock_t idr_lock;
>   	struct idr lcids;
> @@ -288,15 +288,14 @@ static int qcom_glink_tx(struct qcom_glink *glink,
>   			 const void *data, size_t dlen, bool wait)
>   {
>   	unsigned int tlen = hlen + dlen;
> +	unsigned long flags;
>   	int ret;
>   
>   	/* Reject packets that are too big */
>   	if (tlen >= glink->tx_pipe->length)
>   		return -EINVAL;
>   
> -	ret = mutex_lock_interruptible(&glink->tx_lock);
> -	if (ret)
> -		return ret;
> +	spin_lock_irqsave(&glink->tx_lock, flags);
>   
>   	while (qcom_glink_tx_avail(glink) < tlen) {
>   		if (!wait) {
> @@ -304,7 +303,12 @@ static int qcom_glink_tx(struct qcom_glink *glink,
>   			goto out;
>   		}
>   
> +		/* Wait without holding the tx_lock */
> +		spin_unlock_irqrestore(&glink->tx_lock, flags);
> +
>   		usleep_range(10000, 15000);
> +
> +		spin_lock_irqsave(&glink->tx_lock, flags);
>   	}
>   
>   	qcom_glink_tx_write(glink, hdr, hlen, data, dlen);
> @@ -313,7 +317,7 @@ static int qcom_glink_tx(struct qcom_glink *glink,
>   	mbox_client_txdone(glink->mbox_chan, 0);
>   
>   out:
> -	mutex_unlock(&glink->tx_lock);
> +	spin_unlock_irqrestore(&glink->tx_lock, flags);
>   
>   	return ret;
>   }
> @@ -1567,7 +1571,7 @@ struct qcom_glink *qcom_glink_native_probe(struct device *dev,
>   	glink->features = features;
>   	glink->intentless = intentless;
>   
> -	mutex_init(&glink->tx_lock);
> +	spin_lock_init(&glink->tx_lock);
>   	spin_lock_init(&glink->rx_lock);
>   	INIT_LIST_HEAD(&glink->rx_queue);
>   	INIT_WORK(&glink->rx_work, qcom_glink_work);
>