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serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs

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[ 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>
This commit is contained in:
Vignesh Raghavendra 2021-06-22 20:27:04 +05:30 committed by Greg Kroah-Hartman
parent e0e3e0b7da
commit 9443acbd25
1 changed files with 19 additions and 1 deletions
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20
drivers/tty/serial/8250/8250_omap.c
View File

@ -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 = {