linux-kernel - Re: [PATCH V2] accel/amdxdna: Check interrupt register before mailbox_rx

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Message-ID: <41667dcc-b57d-44ff-99cf-5a91dbec1e56@linux.intel.com>
Date: Thu, 27 Feb 2025 09:36:49 +0100
From: Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>
To: Lizhi Hou <lizhi.hou@....com>, ogabbay@...nel.org,
 quic_jhugo@...cinc.com, Mario.Limonciello@....com,
 dri-devel@...ts.freedesktop.org
Cc: linux-kernel@...r.kernel.org, min.ma@....com, max.zhen@....com,
 sonal.santan@....com, king.tam@....com
Subject: Re: [PATCH V2] accel/amdxdna: Check interrupt register before
 mailbox_rx_worker exits

Reviewed-by: Jacek Lawrynowicz <jacek.lawrynowicz@...ux.intel.com>

On 2/26/2025 5:18 PM, Lizhi Hou wrote:
> There is a timeout failure been found during stress tests. If the firmware
> generates a mailbox response right after driver clears the mailbox channel
> interrupt register, the hardware will not generate an interrupt for the
> response. This causes the unexpected mailbox command timeout.
> 
> To handle this failure, driver checks the interrupt register before
> exiting mailbox_rx_worker(). If there is a new response, driver goes back
> to process it.
> 
> Signed-off-by: Lizhi Hou <lizhi.hou@....com>
> ---
>  drivers/accel/amdxdna/amdxdna_mailbox.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/accel/amdxdna/amdxdna_mailbox.c b/drivers/accel/amdxdna/amdxdna_mailbox.c
> index de7bf0fb4594..8651b1d3c3ab 100644
> --- a/drivers/accel/amdxdna/amdxdna_mailbox.c
> +++ b/drivers/accel/amdxdna/amdxdna_mailbox.c
> @@ -348,8 +348,6 @@ static irqreturn_t mailbox_irq_handler(int irq, void *p)
>  	trace_mbox_irq_handle(MAILBOX_NAME, irq);
>  	/* Schedule a rx_work to call the callback functions */
>  	queue_work(mb_chann->work_q, &mb_chann->rx_work);
> -	/* Clear IOHUB register */
> -	mailbox_reg_write(mb_chann, mb_chann->iohub_int_addr, 0);
>  
>  	return IRQ_HANDLED;
>  }
> @@ -366,6 +364,9 @@ static void mailbox_rx_worker(struct work_struct *rx_work)
>  		return;
>  	}
>  
> +again:
> +	mailbox_reg_write(mb_chann, mb_chann->iohub_int_addr, 0);
> +
>  	while (1) {
>  		/*
>  		 * If return is 0, keep consuming next message, until there is
> @@ -379,10 +380,18 @@ static void mailbox_rx_worker(struct work_struct *rx_work)
>  		if (unlikely(ret)) {
>  			MB_ERR(mb_chann, "Unexpected ret %d, disable irq", ret);
>  			WRITE_ONCE(mb_chann->bad_state, true);
> -			disable_irq(mb_chann->msix_irq);
> -			break;
> +			return;
>  		}
>  	}
> +
> +	/*
> +	 * The hardware will not generate interrupt if firmware creates a new
> +	 * response right after driver clears interrupt register. Check
> +	 * the interrupt register to make sure there is not any new response
> +	 * before exiting.
> +	 */
> +	if (mailbox_reg_read(mb_chann, mb_chann->iohub_int_addr))
> +		goto again;
>  }
>  
>  int xdna_mailbox_send_msg(struct mailbox_channel *mb_chann,