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authorPhilipp Zabel <p.zabel@pengutronix.de>2015-05-19 04:54:09 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-05-24 15:43:29 -0400
commit392bceedb107a3dc1d4287e63d7670d08f702feb (patch)
tree0d3cd424df497b26be3eef6791e33dc32c29fa71
parent43dd1f9a5b05d6db2cb258354a01ace63baa5c0b (diff)
serial: imx: Fix DMA handling for IDLE condition aborts
The driver configures the IDLE condition to interrupt the SDMA engine. Since the SDMA UART ROM script doesn't clear the IDLE bit itself, this caused repeated 1-byte DMA transfers, regardless of available data in the RX FIFO. Also, when returning due to the IDLE condition, the UART ROM script already increased its counter, causing residue to be off by one. This patch clears the IDLE condition to avoid repeated 1-byte DMA transfers and decreases count by when the DMA transfer was aborted due to the IDLE condition, fixing serial transfers using DMA on i.MX6Q. Reported-by: Peter Seiderer <ps.report@gmx.net> Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de> Tested-by: Fabio Estevam <fabio.estevam@freescale.com> Cc: stable <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/tty/serial/imx.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index c8cfa0637128..88250395b0ce 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -911,6 +911,14 @@ static void dma_rx_callback(void *data)
911 911
912 status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state); 912 status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state);
913 count = RX_BUF_SIZE - state.residue; 913 count = RX_BUF_SIZE - state.residue;
914
915 if (readl(sport->port.membase + USR2) & USR2_IDLE) {
916 /* In condition [3] the SDMA counted up too early */
917 count--;
918
919 writel(USR2_IDLE, sport->port.membase + USR2);
920 }
921
914 dev_dbg(sport->port.dev, "We get %d bytes.\n", count); 922 dev_dbg(sport->port.dev, "We get %d bytes.\n", count);
915 923
916 if (count) { 924 if (count) {