Re: [PATCH v4] serial: 8250_omap: Implementation of Errata i2310

Raghavendra, Vignesh
2024-06-24T17:09:17Z

On 6/24/2024 10:26 PM, Udit Kumar wrote:
> As per Errata i2310[0], Erroneous timeout can be triggered,
> if this Erroneous interrupt is not cleared then it may leads
> to storm of interrupts, therefore apply Errata i2310 solution.
>
> [0] https://www.ti.com/lit/pdf/sprz536 page 23
>
> Fixes: b67e830d38fa ("serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs")
> Cc: stable@vger.kernel.org
> Signed-off-by: Udit Kumar <u-kumar1@ti.com>
> ---

[...]

>
> diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c
> index 170639d12b2a..1af9aed99c65 100644
> --- a/drivers/tty/serial/8250/8250_omap.c
> +++ b/drivers/tty/serial/8250/8250_omap.c
> @@ -115,6 +115,10 @@
> /* RX FIFO occupancy indicator */
> #define UART_OMAP_RX_LVL 0x19
>
> +/* Timeout low and High */
> +#define UART_OMAP_TO_L 0x26
> +#define UART_OMAP_TO_H 0x27
> +
> /*
> * Copy of the genpd flags for the console.
> * Only used if console suspend is disabled
> @@ -663,13 +667,25 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id)
>
> /*
> * 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.
> + * FIFO has been drained or erroneously.
> + * So apply solution of Errata i2310 as mentioned in
> + * https://www.ti.com/lit/pdf/sprz536
> */
> 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);
> + unsigned char efr2, timeout_h, timeout_l;
> +
> + efr2 = serial_in(up, UART_OMAP_EFR2);
> + timeout_h = serial_in(up, UART_OMAP_TO_H);
> + timeout_l = serial_in(up, UART_OMAP_TO_L);
> + serial_out(up, UART_OMAP_TO_H, 0xFF);
> + serial_out(up, UART_OMAP_TO_L, 0xFF);
> + serial_out(up, UART_OMAP_EFR2, UART_OMAP_EFR2_TIMEOUT_BEHAVE);
> + serial_in(up, UART_IIR);
> + serial_out(up, UART_OMAP_EFR2, efr2);
> + serial_out(up, UART_OMAP_TO_H, timeout_h);
> + serial_out(up, UART_OMAP_TO_L, timeout_l);
> }
>
> /* Stop processing interrupts on input overrun */

Reviewed-by: Vignesh Raghavendra <vigneshr@ti.com>