| Message ID | 20210622145704.11168-1-vigneshr@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs | expand |
On 22.06.21 16:57, Vignesh Raghavendra wrote: > 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> > Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> > --- > 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@ti.com > > 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 = { > Tested-by: Jan Kiszka <jan.kiszka@siemens.com> Thanks, Jan
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 = {
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> Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com> --- 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@ti.com drivers/tty/serial/8250/8250_omap.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-)