DW UART sometimes triggers IIR_RDI during DMA Rx when IIR_RX_TIMEOUT
should have been triggered instead. Since IIR_RDI has higher priority
than IIR_RX_TIMEOUT, this causes the Rx to hang into interrupt loop.
The problem seems to occur at least with some combinations of
small-sized transfers (I've reproduced the problem on Elkhart Lake PSE
UARTs).
If there's already an on-going Rx DMA and IIR_RDI triggers, fall
graciously back to non-DMA Rx. That is, behave as if IIR_RX_TIMEOUT had
occurred.
8250_omap already considers IIR_RDI similar to this change so its
nothing unheard of.
Fixes: 75df022b5f89 ("serial: 8250_dma: Fix RX handling")
Cc: <stable@xxxxxxxxxxxxxxx>
Co-developed-by: Srikanth Thokala <srikanth.thokala@xxxxxxxxx>
Signed-off-by: Srikanth Thokala <srikanth.thokala@xxxxxxxxx>
Co-developed-by: Aman Kumar <aman.kumar@xxxxxxxxx>
Signed-off-by: Aman Kumar <aman.kumar@xxxxxxxxx>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_port.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index fe8662cd9402..92dd18716169 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -1897,6 +1897,10 @@ EXPORT_SYMBOL_GPL(serial8250_modem_status);
static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
{
switch (iir & 0x3f) {
+ case UART_IIR_RDI:
+ if (!up->dma->rx_running)
+ break;
+ fallthrough;
case UART_IIR_RX_TIMEOUT:
serial8250_rx_dma_flush(up);
fallthrough;
--
2.30.2
