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

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>
---
Test logs:
https://gist.github.com/uditkumarti/48e239540db4e761861fbd1d7d31cfed

Change logs
Changes in v4:
- Reverted fifo empty check before applying errata
Link to v3:
https://lore.kernel.org/all/20240619105903.165434-1-u-kumar1@ti.com/

Changes in v3:
- CC stable in commit message
Link to v2:
https://lore.kernel.org/all/20240617052253.2188140-1-u-kumar1@ti.com/

Changes in v2:
- Added Fixes Tag and typo correction in commit message
- Corrected bit position to UART_OMAP_EFR2_TIMEOUT_BEHAVE
Link to v1
https://lore.kernel.org/all/20240614061314.290840-1-u-kumar1@ti.com/

 drivers/tty/serial/8250/8250_omap.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

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>

On Mon, Jun 24, 2024 at 10:26:56PM +0530, 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>

As I have already taken the v3 patch to my tree, please send a "fix"
patch on top of it, as I can not rebase a public tree.

thanks,

greg k-h

Thanks Greg

On 6/25/2024 10:10 AM, Greg KH wrote:
> On Mon, Jun 24, 2024 at 10:26:56PM +0530, 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>
> As I have already taken the v3 patch to my tree, please send a "fix"
> patch on top of it, as I can not rebase a public tree.


I posted delta patch on top

https://lore.kernel.org/all/20240625051338.2761599-1-u-kumar1@ti.com/


> thanks,
>
> greg k-h