[PATCH 1/7] serial: imx: only set DMA rx-ing when DMA starts
From: Uwe Kleine-König <hidden>
Date: 2017-07-03 06:48:50
Also in:
linux-serial, lkml
Hello, On Fri, Jun 30, 2017 at 02:04:40PM +0200, Romain Perier wrote:
From: Nandor Han <redacted> Avoid the situation when `dma_is_rxing` could incorrectly signal that DMA RX channel is receiving data in case DMA preparation or sg mapping fails.
Just from reading the commit log and the patch I didn't understand the problem that is supposed to be fixed here. After looking at it for some I understood. I don't suggest a new commit log here as it has to look different if you pick up my comment below.
quoted hunk ↗ jump to hunk
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c index 5437b34..1d35293 100644 --- a/drivers/tty/serial/imx.c +++ b/drivers/tty/serial/imx.c@@ -725,11 +725,11 @@ static irqreturn_t imx_rxint(int irq, void *dev_id) return IRQ_HANDLED; } -static void imx_disable_rx_int(struct imx_port *sport) +static void imx_disable_rx_int(struct imx_port *sport, bool is_rxing) { unsigned long temp; - sport->dma_is_rxing = 1; + sport->dma_is_rxing = is_rxing; /* disable the receiver ready and aging timer interrupts */ temp = readl(sport->port.membase + UCR1);@@ -762,7 +762,7 @@ static void imx_dma_rxint(struct imx_port *sport) temp = readl(sport->port.membase + USR2); if ((temp & USR2_RDR) && !sport->dma_is_rxing) { - imx_disable_rx_int(sport); + imx_disable_rx_int(sport, false); /* tell the DMA to receive the data. */ start_rx_dma(sport);@@ -1083,6 +1083,7 @@ static int start_rx_dma(struct imx_port *sport) desc->callback_param = sport; dev_dbg(dev, "RX: prepare for the DMA.\n"); + sport->dma_is_rxing = 1; sport->rx_cookie = dmaengine_submit(desc); dma_async_issue_pending(chan); return 0;@@ -1362,7 +1363,7 @@ static int imx_startup(struct uart_port *port) spin_unlock(&tty->files_lock); if (readcnt > 0) { - imx_disable_rx_int(sport); + imx_disable_rx_int(sport, true);
I wonder if it would be saner to not assign to dma_is_rxing in imx_disable_rx_int() at all but do this only in start_rx_dma() and imx_dma_rxint(). Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |