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mailbox: Support blocking transfers in atomic context

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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@nvidia.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
This commit is contained in:
Thierry Reding 2018-11-28 10:54:10 +01:00 committed by Jassi Brar
parent 2298a6f09f
commit a8803d7421
3 changed files with 33 additions and 0 deletions
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28
drivers/mailbox/mailbox.c
View File

@ -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.

1
include/linux/mailbox_client.h
View File

@ -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 */

4
include/linux/mailbox_controller.h
View File

@ -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);