On K3 family of SoCs (which includes AM654 SoC), it is observed that RX
TIMEOUT is signalled after RX FIFO has been drained, in which case a
dummy read of RX FIFO is required to clear RX TIMEOUT condition.
Otherwise, this would lead to an interrupt storm.
Fix this by introducing UART_RX_TIMEOUT_QUIRK flag and doing a dummy
read in IRQ handler when RX TIMEOUT is reported with no data in RX FIFO.
Fixes: be70874498f3 ("serial: 8250_omap: Add support for AM654 UART controller")
Reported-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Signed-off-by: Vignesh Raghavendra <vigneshr@xxxxxx>
---
v2:
Restrict workaround to K3 family of devices only (ti,am654-uart) where
issue was reported.
v1: https://lore.kernel.org/r/20210511151955.28071-1-vigneshr@xxxxxx
drivers/tty/serial/8250/8250_omap.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
index c06631ced414..79418d4beb48 100644
--- a/drivers/tty/serial/8250/8250_omap.c
+++ b/drivers/tty/serial/8250/8250_omap.c
@@ -43,6 +43,7 @@
#define UART_ERRATA_CLOCK_DISABLE (1 << 3)
#define UART_HAS_EFR2 BIT(4)
#define UART_HAS_RHR_IT_DIS BIT(5)
+#define UART_RX_TIMEOUT_QUIRK BIT(6)
#define OMAP_UART_FCR_RX_TRIG 6
#define OMAP_UART_FCR_TX_TRIG 4
@@ -104,6 +105,9 @@
#define UART_OMAP_EFR2 0x23
#define UART_OMAP_EFR2_TIMEOUT_BEHAVE BIT(6)
+/* RX FIFO occupancy indicator */
+#define UART_OMAP_RX_LVL 0x64
+
struct omap8250_priv {
int line;
u8 habit;
@@ -611,6 +615,7 @@ static int omap_8250_dma_handle_irq(struct uart_port *port);
static irqreturn_t omap8250_irq(int irq, void *dev_id)
{
struct uart_port *port = dev_id;
+ struct omap8250_priv *priv = port->private_data;
struct uart_8250_port *up = up_to_u8250p(port);
unsigned int iir;
int ret;
@@ -625,6 +630,18 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
serial8250_rpm_get(up);
iir = serial_port_in(port, UART_IIR);
ret = serial8250_handle_irq(port, iir);
+
+ /*
+ * On K3 SoCs, it is observed that RX TIMEOUT is signalled after
+ * FIFO has been drained, in which case a dummy read of RX FIFO
+ * is required to clear RX TIMEOUT condition.
+ */
+ if (priv->habit & UART_RX_TIMEOUT_QUIRK &&
+ (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT &&
+ serial_port_in(port, UART_OMAP_RX_LVL) == 0) {
+ serial_port_in(port, UART_RX);
+ }
+
serial8250_rpm_put(up);
return IRQ_RETVAL(ret);
@@ -1218,7 +1235,8 @@ static struct omap8250_dma_params am33xx_dma = {
static struct omap8250_platdata am654_platdata = {
.dma_params = &am654_dma,
- .habit = UART_HAS_EFR2 | UART_HAS_RHR_IT_DIS,
+ .habit = UART_HAS_EFR2 | UART_HAS_RHR_IT_DIS |
+ UART_RX_TIMEOUT_QUIRK,
};
static struct omap8250_platdata am33xx_platdata = {
--
2.32.0
