rpmsg: glink: Use spinlock in tx path

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.

Tested-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

1 files changed, 11 insertions, 7 deletions

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index e0f31ed096a5..768ef542a841 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;
-        int ret;
+        unsigned long flags;
+        int ret = 0;
 
         /* 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);