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serial: 8250: Don't service RX FIFO if interrupts are disabled
Currently, data in RX FIFO is read based on UART_LSR register state even if RDI and RLSI interrupts are disabled in UART_IER register. This is because when IRQ handler is called due to TX FIFO empty event, RX FIFO is serviced based on UART_LSR register status instead of UART_IIR status. This defeats the purpose of disabling UART RX FIFO interrupts during throttling(see, omap_8250_throttle()) as IRQ handler continues to drain UART RX FIFO resulting in overflow of buffer at tty layer. Fix this by making sure that driver drains UART RX FIFO only when UART_IIR_RDI is set along with UART_LSR_BI or UART_LSR_DR bits. Signed-off-by: Vignesh R <vigneshr@ti.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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1 changed files with 2 additions and 1 deletions
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@ -1854,7 +1854,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
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status = serial_port_in(port, UART_LSR);
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if (status & (UART_LSR_DR | UART_LSR_BI)) {
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if (status & (UART_LSR_DR | UART_LSR_BI) &&
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iir & UART_IIR_RDI) {
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if (!up->dma || handle_rx_dma(up, iir))
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status = serial8250_rx_chars(up, status);
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}
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