serial: samsung: Clear operation mode on UART shutdown
Exynos serial ports operate either in a DMA-based or interrupt-based modes. In DMA-based mode, the UART generates a transfer data request and a Transmission (Tx) interrupt in interrupt-based mode. The Tx IRQ is only unmasked in interrupt-based mode and it was done in s3c24xx_serial_start_tx(). Commitba019a3e2a
("serial: samsung: remove redundant interrupt enabling") removed the IRQ enable on that function since it is enabled when the mode is set in enable_tx_pio(). The problem is that enable_tx_pio() is only called if the port mode has not been set before but the mode was not cleared on .shutdown(). So if the UART was shutdown and then started up again, the mode set will remain and the Tx IRQ won't be unmasked. This caused a hang on at least Exynos5250, Exynos5420 and Exynos5800 when the system is rebooted or powered off. Fixes:ba019a3e2a
("serial: samsung: remove redundant interrupt enabling") Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk> Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -963,6 +963,7 @@ static void s3c24xx_serial_shutdown(struct uart_port *port)
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free_irq(ourport->tx_irq, ourport);
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tx_enabled(port) = 0;
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ourport->tx_claimed = 0;
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ourport->tx_mode = 0;
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}
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if (ourport->rx_claimed) {
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