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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>
This commit is contained in:
Vignesh R 2018-02-08 18:25:41 +05:30 committed by Greg Kroah-Hartman
parent 890fb16b4c
commit 2e9fe53910
1 changed files with 2 additions and 1 deletions
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3
drivers/tty/serial/8250/8250_port.c
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@ -1854,7 +1854,8 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
status = serial_port_in(port, UART_LSR);
if (status & (UART_LSR_DR | UART_LSR_BI)) {
if (status & (UART_LSR_DR | UART_LSR_BI) &&
iir & UART_IIR_RDI) {
if (!up->dma || handle_rx_dma(up, iir))
status = serial8250_rx_chars(up, status);
}