From c0a04ee8cd0e7c8bb3cdb9f206f5be7697d23b83 Mon Sep 17 00:00:00 2001 From: Philipp Zabel Date: Tue, 19 May 2015 10:54:09 +0200 Subject: [PATCH] serial: imx: Fix DMA handling for IDLE condition aborts commit 392bceedb107a3dc1d4287e63d7670d08f702feb upstream. 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 Signed-off-by: Philipp Zabel Tested-by: Fabio Estevam Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/imx.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 23061918b0e4c..f74f400fcb57a 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c @@ -959,6 +959,14 @@ static void dma_rx_callback(void *data) status = dmaengine_tx_status(chan, (dma_cookie_t)0, &state); count = RX_BUF_SIZE - state.residue; + + if (readl(sport->port.membase + USR2) & USR2_IDLE) { + /* In condition [3] the SDMA counted up too early */ + count--; + + writel(USR2_IDLE, sport->port.membase + USR2); + } + dev_dbg(sport->port.dev, "We get %d bytes.\n", count); if (count) { -- 2.47.2