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Commit 04ed8080 authored by Neeraj Upadhyay's avatar Neeraj Upadhyay Committed by Srinivas Ramana
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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: default avatarNeeraj Upadhyay <neeraju@codeaurora.org>
parent a5228cf6

drivers/tty/serial/msm_serial.c

+13 −13
Original line number Diff line number Diff line
@@ -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;

}