tty: serial: msm: Move request_irq to the end of startup

Move the request_irq() call to the end of the msm_startup(),
so that we don't handle interrupts while msm_startup() is
running. This avoids potential races while initialization
is in progress. For example, consider below scenario
where rx handler reads the intermediate value of dma->chan,
set in msm_request_rx_dma(), and tries to do dma mapping,
which results in data abort.

uart_port_startup()
  msm_startup()
   request_irq()
   ...
   msm_request_rx_dma()
    ...
    dma->chan = dma_request_slave_channel_reason(dev, "rx");
    <UART RX IRQ>
     msm_uart_irq()
      msm_handle_rx_dm()
       msm_start_rx_dma()
        dma->desc = dma_map_single()
         <data abort>


Change-Id: I94113fe1ebe400f9bb0113922ebc5d257124e34a
Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>

1 files changed, 13 insertions, 13 deletions

diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
index db329230c7ca..75956a8854a2 100644
--- a/drivers/tty/serial/msm_serial.c
+++ b/drivers/tty/serial/msm_serial.c
@@ -1166,26 +1166,17 @@ static int msm_startup(struct uart_port *port)
 	snprintf(msm_port->name, sizeof(msm_port->name),
 		 "msm_serial%d", port->line);
 
-	ret = request_irq(port->irq, msm_uart_irq, IRQF_TRIGGER_HIGH,
-			  msm_port->name, port);
-	if (unlikely(ret))
-		return ret;
-
 	/*
 	 * UART clk must be kept enabled to
 	 * avoid losing received character
 	 */
 	ret = clk_prepare_enable(msm_port->clk);
-	if (ret) {
-		goto err_clk;
+	if (ret)
 		return ret;
-	}
 
 	ret = clk_prepare_enable(msm_port->pclk);
-	if (ret) {
+	if (ret)
 		goto err_pclk;
-		return ret;
-	}
 
 	msm_serial_set_mnd_regs(port);
 
@@ -1213,12 +1204,21 @@ static int msm_startup(struct uart_port *port)
 		msm_request_rx_dma(msm_port, msm_port->uart.mapbase);
 	}
 
+	ret = request_irq(port->irq, msm_uart_irq, IRQF_TRIGGER_HIGH,
+			  msm_port->name, port);
+	if (unlikely(ret))
+		goto err_irq;
+
 	return 0;
 
+err_irq:
+	if (msm_port->is_uartdm)
+		msm_release_dma(msm_port);
+
+	clk_disable_unprepare(msm_port->pclk);
+
 err_pclk:
 	clk_disable_unprepare(msm_port->clk);
-err_clk:
-	free_irq(port->irq, port);
 
 	return ret;
 }