Commit 4d691f75 authored Aug 07, 2017 by Neeraj Upadhyay Committed by Greg Kroah-Hartman Aug 28, 2017

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>

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Reviewd-by: Andy Gross <andy.gross@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 62f466ee

drivers/tty/serial/msm_serial.c

+14 −5

Original line number	Diff line number	Diff line
		@@ -1175,11 +1175,6 @@ 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;

		msm_init_clock(port);

		if (likely(port->fifosize > 12))
		@@ -1206,7 +1201,21 @@ 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);
		clk_disable_unprepare(msm_port->clk);

		return ret;
		}

		static void msm_shutdown(struct uart_port *port)

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