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| author | Jiada Wang | 2014-12-09 10:11:29 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman | 2015-01-09 23:23:07 +0100 |
| commit | d64b8607aceb9bd3b3dabddfc4f76458e5a8489d (patch) | |
| tree | 12a74a895defc98a81441333bcedfd8c776031f4 /drivers/tty/serial | |
| parent | serial: imx: use dma_is_txing to synchronize dma_tx_callback and imx_dma_tx (diff) | |
| download | kernel-qcow2-linux-d64b8607aceb9bd3b3dabddfc4f76458e5a8489d.tar.gz kernel-qcow2-linux-d64b8607aceb9bd3b3dabddfc4f76458e5a8489d.tar.xz kernel-qcow2-linux-d64b8607aceb9bd3b3dabddfc4f76458e5a8489d.zip | |
Revert "serial: imx: always wake up the processes in the TX callback"
This reverts commit 2ad28e3efee21a5bbf940c83d1f0395b76bd3efb.
Instead of always wake up write_wait process in TX callback,
TX callback should call imx_dma_tx() again, and let imx_dma_tx
transfer the remaining data in circle buffer.
The issue with commit 2ad28e3 is, in case there is remaining
data in circle buffer, but no process is waiting on write_wait
queue, then as no following uart_write() will be called after
uart_write_wakeup(), thus cause data loss.
Moreover according to Documentation/serial/driver, uart_write_wakeup()
should be called in case the transmit buffer have dropped below
a threshold.
Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/serial')
| -rw-r--r-- | drivers/tty/serial/imx.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 1c4f367b6fb6..73158d96822a 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -516,7 +516,8 @@ static void dma_tx_callback(void *data) spin_unlock_irqrestore(&sport->port.lock, flags); - uart_write_wakeup(&sport->port); + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS) + uart_write_wakeup(&sport->port); if (waitqueue_active(&sport->dma_wait)) { wake_up(&sport->dma_wait); |