linux-kernel - Re: [PATCH v2] bus: omap_l3_smx: identify timeout source before rebooting

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Message-ID: <20230731221640.6lugeimfg4f53rs2@mercury.elektranox.org>
Date:   Tue, 1 Aug 2023 00:16:40 +0200
From:   Sebastian Reichel <sre@...nel.org>
To:     "Sicelo A. Mhlongo" <absicsz@...il.com>
Cc:     linux-omap@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tony Lindgren <tony@...mide.com>
Subject: Re: [PATCH v2] bus: omap_l3_smx: identify timeout source before
 rebooting

Hi,

On Mon, Jul 31, 2023 at 11:03:47PM +0200, Sicelo A. Mhlongo wrote:
> Identify and print the error source before rebooting the board due
> to an l3 application timeout error, by delaying the BUG_ON. This
> is helpful when debugging, e.g. via serial.
> 
> Signed-off-by: Sicelo A. Mhlongo <absicsz@...il.com>
> ---
>  drivers/bus/omap_l3_smx.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/bus/omap_l3_smx.c b/drivers/bus/omap_l3_smx.c
> index bb1606f5ce2d..0ccde12e33c0 100644
> --- a/drivers/bus/omap_l3_smx.c
> +++ b/drivers/bus/omap_l3_smx.c
> @@ -170,11 +170,9 @@ static irqreturn_t omap3_l3_app_irq(int irq, void *_l3)
>  		status = omap3_l3_readll(l3->rt, L3_SI_FLAG_STATUS_0);
>  		/*
>  		 * if we have a timeout error, there's nothing we can
> -		 * do besides rebooting the board. So let's BUG on any
> -		 * of such errors and handle the others. timeout error
> -		 * is severe and not expected to occur.
> +		 * do besides rebooting the board after identifying the
> +		 * error source.
>  		 */
> -		BUG_ON(status & L3_STATUS_0_TIMEOUT_MASK);
>  	} else {
>  		status = omap3_l3_readll(l3->rt, L3_SI_FLAG_STATUS_1);
>  		/* No timeout error for debug sources */

I think it's sensible to just remove the comments from both if/else
branches. They no longer make sense in this place. Afterwards you
should remove the curly brackets to follow kernel coding style.

> @@ -190,6 +188,12 @@ static irqreturn_t omap3_l3_app_irq(int irq, void *_l3)
>  		ret |= omap3_l3_block_irq(l3, error, error_addr);
>  	}
>  
> +	/*
> +	 * BUG on application timeout errors since they are severe and not
> +	 * expected to occur.
> +	 */

I suggest using the original text. It does mention "there's nothing
we can do besides rebooting the board".

> +	BUG_ON(!int_type && status & L3_STATUS_0_TIMEOUT_MASK);
> +
>  	/* Clear the status register */
>  	clear = (L3_AGENT_STATUS_CLEAR_IA << int_type) |
>  		L3_AGENT_STATUS_CLEAR_TA;

-- Sebastian

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