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tty:serial:msm:Do not restore Rx interrupts in DMA 

Avoid data corruption issues that result in CRC errors during file
transfers over serial ports at higher baud rates.

The current msm_serial driver masks the FIFO Rx interrupts in
msm_start_rx_dma() since Rx FIFO interrupts are not required in DMA
mode. However, msm_complete_rx_dma() re-enables the Rx FIFO interrupts
which could cause RXSTALE event to be processed when a TXLEV interrupt
occurs.

The following is the sequence of events that could occur resulting in
data corruption.

msm_start_rx_dma -> msm_complete_rx_dma -->
spin_unlock_irqrestore(&port->lock) -->
msm_uart_irq()(For TXLEV interrupt) -->  msm_handle_rx_dm() (Read from
FIFO resulting in data corruption)

The patch fixes the issue by not restoring the RXLEV and RXSTALE
interrupts in msm_complete_rx_dma(). These interrupts are required only
in FIFO mode.

Signed-off-by: Charanya Venkatraman <charanya@codeaurora.org>
Acked-by: Andy Gross <andy.gross@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Charanya Venkatraman 2016-06-07 15:58:41 +05:30 committed by Greg Kroah-Hartman
parent e4276ff8a0
commit 002eb41f30
1 changed files with 0 additions and 4 deletions
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4
drivers/tty/serial/msm_serial.c
View File

@ -557,10 +557,6 @@ static void msm_complete_rx_dma(void *args)
val &= ~dma->enable_bit;
msm_write(port, val, UARTDM_DMEN);
/* Restore interrupts */
msm_port->imr |= UART_IMR_RXLEV | UART_IMR_RXSTALE;
msm_write(port, msm_port->imr, UART_IMR);
if (msm_read(port, UART_SR) & UART_SR_OVERRUN) {
port->icount.overrun++;
tty_insert_flip_char(tport, 0, TTY_OVERRUN);