Hi Hari,
On Thursday, October 14, 2010 9:13 PM Kanigeri, Hari wrote:
> Schedule the Tasklet to send only when mailbox fifo is full, else
> send the message in the Process context. This would avoid
> needless scheduling of Tasklet for every message transfer
>
> Signed-off-by: Hari Kanigeri <h-kanigeri2@xxxxxx>
> ---
> arch/arm/plat-omap/mailbox.c | 9 +++++++--
> 1 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/plat-omap/mailbox.c b/arch/arm/plat-omap/mailbox.c
> index ed960c1..a4170c7 100644
> --- a/arch/arm/plat-omap/mailbox.c
> +++ b/arch/arm/plat-omap/mailbox.c
> @@ -92,20 +92,25 @@ int omap_mbox_msg_send(struct omap_mbox *mbox,
> mbox_msg_t msg) struct omap_mbox_queue *mq = mbox->txq;
> int ret = 0, len;
>
> - spin_lock(&mq->lock);
> + spin_lock_bh(&mq->lock);
>
Please check if this scenario looks valid to you, as discussed and depicted
with Fernando:
Supposing that at this point the hw fifo is full and there are messages in
the kfifo.
> if (kfifo_avail(&mq->fifo) < sizeof(msg)) {
> ret = -ENOMEM;
> goto out;
> }
>
We reach this point.
In this scenario, the DSP or other Core reads a message from the mbox hw fifo.
The next happens:
1.- The not full interrupt is triggered to the MPU.
2.- The mbox's ISR schedules the tasklet to write the message.
3.- The ISR is left and returns to here (since we still have the bh lock the
tasklet won't run).
> + if (!__mbox_poll_for_space(mbox)) {\
4.- We check for mbox_fifo_full and we have space. so the message is written.
> + mbox_fifo_write(mbox, msg);
At this point it looks that the FIFO order is lost. We write this message
before the ones in the kfifo.
A solution for this could be checking if there are messages in the kfifo
before trying to write directly to the hw fifo, if so, just continue
scheduling the tasklet.
> + goto out;
> + }
> +
> len = kfifo_in(&mq->fifo, (unsigned char *)&msg, sizeof(msg));
> WARN_ON(len != sizeof(msg));
>
> tasklet_schedule(&mbox->txq->tasklet);
>
> out:
> - spin_unlock(&mq->lock);
> + spin_unlock_bh(&mq->lock);
> return ret;
> }
> EXPORT_SYMBOL(omap_mbox_msg_send);
> --
> 1.7.0--
To unsubscribe from this list: send the line "unsubscribe linux-omap" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
