| From 26cf89bf2f4c5d85f881476b55233c56c7d64300 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Tue, 22 Jun 2021 20:27:04 +0530 |
| Subject: serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs |
| |
| From: Vignesh Raghavendra <vigneshr@ti.com> |
| |
| [ Upstream commit b67e830d38fa9335d927fe67e812e3ed81b4689c ] |
| |
| 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@siemens.com> |
| Tested-by: Jan Kiszka <jan.kiszka@siemens.com> |
| Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> |
| Link: https://lore.kernel.org/r/20210622145704.11168-1-vigneshr@ti.com |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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 a9cfe1c57642..95e2d6de4f21 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; |
| @@ -598,6 +602,7 @@ 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; |
| @@ -612,6 +617,18 @@ 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); |
| @@ -1210,7 +1227,8 @@ 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 = { |
| -- |
| 2.30.2 |
| |