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