From: Philipp Zabel Date: Tue, 19 May 2015 08:54:09 +0000 (+0200) Subject: serial: imx: Fix DMA handling for IDLE condition aborts X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=392bceedb107a3dc1d4287e63d7670d08f702feb;p=linux-beck.git 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 Signed-off-by: Philipp Zabel Tested-by: Fabio Estevam Cc: stable Signed-off-by: Greg Kroah-Hartman --- 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) 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) {