From: Thierry Reding <treding@xxxxxxxxxx>
The mailbox framework supports blocking transfers via completions for
clients that can sleep. In order to support blocking transfers in cases
where the transmission is not permitted to sleep, add a new ->flush()
callback that controller drivers can implement to busy loop until the
transmission has been completed. A new mbox_flush() function can be
called by mailbox consumers in atomic context to make sure a transfer
has completed.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
Changes in v3:
- add explicit mailbox flush API
---
drivers/mailbox/mailbox.c | 28 ++++++++++++++++++++++++++++
include/linux/mailbox_client.h | 1 +
include/linux/mailbox_controller.h | 4 ++++
3 files changed, 33 insertions(+)
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index eb781e2b19cb..044e24804767 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -283,6 +283,34 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg)
}
EXPORT_SYMBOL_GPL(mbox_send_message);
+/**
+ * mbox_flush - flush a mailbox channel
+ * @chan: mailbox channel to flush
+ * @timeout: time, in milliseconds, to allow the flush operation to succeed
+ *
+ * Mailbox controllers that need to work in atomic context can implement the
+ * ->flush() callback to busy loop until a transmission has been completed.
+ * The implementation must call mbox_chan_txdone() upon success. Clients can
+ * call the mbox_flush() function at any time after mbox_send_message() to
+ * flush the transmission. After the function returns success, the mailbox
+ * transmission is guaranteed to have completed.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int mbox_flush(struct mbox_chan *chan, unsigned long timeout)
+{
+ int ret;
+
+ if (!chan->mbox->ops->flush)
+ return -ENOTSUPP;
+
+ ret = chan->mbox->ops->flush(chan, timeout);
+ if (ret < 0)
+ tx_tick(chan, ret);
+
+ return ret;
+}
+
/**
* mbox_request_channel - Request a mailbox channel.
* @cl: Identity of the client requesting the channel.
diff --git a/include/linux/mailbox_client.h b/include/linux/mailbox_client.h
index 44348710953f..faa7da3c9c8b 100644
--- a/include/linux/mailbox_client.h
+++ b/include/linux/mailbox_client.h
@@ -44,6 +44,7 @@ struct mbox_chan *mbox_request_channel_byname(struct mbox_client *cl,
const char *name);
struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index);
int mbox_send_message(struct mbox_chan *chan, void *mssg);
+int mbox_flush(struct mbox_chan *chan, unsigned long timeout);
void mbox_client_txdone(struct mbox_chan *chan, int r); /* atomic */
bool mbox_client_peek_data(struct mbox_chan *chan); /* atomic */
void mbox_free_channel(struct mbox_chan *chan); /* may sleep */
diff --git a/include/linux/mailbox_controller.h b/include/linux/mailbox_controller.h
index 9b0b21207345..4994a438444c 100644
--- a/include/linux/mailbox_controller.h
+++ b/include/linux/mailbox_controller.h
@@ -24,6 +24,9 @@ struct mbox_chan;
* transmission of data is reported by the controller via
* mbox_chan_txdone (if it has some TX ACK irq). It must not
* sleep.
+ * @flush: Called when a client requests transmissions to be blocking but
+ * the context doesn't allow sleeping. Typically the controller
+ * will implement a busy loop waiting for the data to flush out.
* @startup: Called when a client requests the chan. The controller
* could ask clients for additional parameters of communication
* to be provided via client's chan_data. This call may
@@ -46,6 +49,7 @@ struct mbox_chan;
*/
struct mbox_chan_ops {
int (*send_data)(struct mbox_chan *chan, void *data);
+ int (*flush)(struct mbox_chan *chan, unsigned long timeout);
int (*startup)(struct mbox_chan *chan);
void (*shutdown)(struct mbox_chan *chan);
bool (*last_tx_done)(struct mbox_chan *chan);
--
2.19.1
