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

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Date: Mon, 24 Jun 2024 22:38:49 +0530
From: "Raghavendra, Vignesh" <vigneshr@...com>
To: Udit Kumar <u-kumar1@...com>, <nm@...com>, <tony@...mide.com>
CC: <gregkh@...uxfoundation.org>, <jirislaby@...nel.org>,
        <ronald.wahl@...itan.com>, <thomas.richard@...tlin.com>,
        <tglx@...utronix.de>, <linux-kernel@...r.kernel.org>,
        <linux-serial@...r.kernel.org>, <ilpo.jarvinen@...ux.intel.com>,
        <stable@...r.kernel.org>
Subject: Re: [PATCH v4] serial: 8250_omap: Implementation of Errata i2310



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@...r.kernel.org
> Signed-off-by: Udit Kumar <u-kumar1@...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@...com>