[PATCH v3 6/6] serial: imx: Fix imx_shutdown procedure

[Martyn Welch]

From: Nandor Han <nandor.han@xxxxxx>

In some cases, it looks that interrupts can happen after the dma was
disabled and port was not yet shutdown. This will result in interrupts
handled by imx_rxint.

This commits updates the shutdown function to ensure that underlying
components are disabled in the right order. This disables RX and TX
blocks, then it disabled interrupts. In case DMA is enabled, it disables
DMA and free corresponding resources. It disables UART port and stop
clocks.

Signed-off-by: Nandor Han <nandor.han@xxxxxx>
Signed-off-by: Romain Perier <romain.perier@xxxxxxxxxxxxx>
Signed-off-by: Martyn Welch <martyn.welch@xxxxxxxxxxxxxxx>
---
 drivers/tty/serial/imx.c | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 256b128..393c1c0 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -1368,44 +1368,40 @@ static void imx_shutdown(struct uart_port *port)
 	unsigned long temp;
 	unsigned long flags;
 
-	if (sport->dma_is_enabled) {
-		sport->dma_is_rxing = 0;
-		sport->dma_is_txing = 0;
-		dmaengine_terminate_sync(sport->dma_chan_tx);
-		dmaengine_terminate_sync(sport->dma_chan_rx);
-
+	if (!sport->port.suspended) {
 		spin_lock_irqsave(&sport->port.lock, flags);
 		imx_stop_tx(port);
 		imx_stop_rx(port);
-		imx_disable_dma(sport);
+
+		if (sport->dma_is_inited && sport->dma_is_enabled)
+			imx_disable_dma(sport);
+
 		spin_unlock_irqrestore(&sport->port.lock, flags);
 		imx_uart_dma_exit(sport);
 	}
 
-	mctrl_gpio_disable_ms(sport->gpios);
-
 	spin_lock_irqsave(&sport->port.lock, flags);
 	temp = readl(sport->port.membase + UCR2);
-	temp &= ~(UCR2_TXEN);
+	temp &= ~(UCR2_TXEN | UCR2_RXEN);
 	writel(temp, sport->port.membase + UCR2);
+	temp = readl(sport->port.membase + UCR4);
+	temp &= ~UCR4_OREN;
+	writel(temp, sport->port.membase + UCR4);
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 
-	/*
-	 * Stop our timer.
-	 */
-	del_timer_sync(&sport->timer);
+	mctrl_gpio_disable_ms(sport->gpios);
 
-	/*
-	 * Disable all interrupts, port and break condition.
-	 */
+	/* Stop our timer. */
+	del_timer_sync(&sport->timer);
 
+	/* Disable port. */
 	spin_lock_irqsave(&sport->port.lock, flags);
 	temp = readl(sport->port.membase + UCR1);
-	temp &= ~(UCR1_TXMPTYEN | UCR1_RRDYEN | UCR1_RTSDEN | UCR1_UARTEN);
-
+	temp &= ~UCR1_UARTEN;
 	writel(temp, sport->port.membase + UCR1);
 	spin_unlock_irqrestore(&sport->port.lock, flags);
 
+	/* Disable clocks. */
 	clk_disable_unprepare(sport->clk_per);
 	clk_disable_unprepare(sport->clk_ipg);
 }
-- 
1.8.3.1