linux-kernel - Re: [PATCH v2] i2c: designware: Fix corrupted memory seen in the ISR

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Message-ID: <a330da0f-e8f5-4703-872b-ae1037d7aed9@linux.intel.com>
Date:   Fri, 15 Sep 2023 15:44:02 +0300
From:   Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:     Jan Bottorff <janb@...amperecomputing.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jan Dabros <jsd@...ihalf.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>
Cc:     linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yann Sionneau <ysionneau@...rayinc.com>
Subject: Re: [PATCH v2] i2c: designware: Fix corrupted memory seen in the ISR

On 9/14/23 02:29, Jan Bottorff wrote:
> Errors were happening in the ISR that looked like corrupted
> memory. This was because memory writes from the core enabling
> interrupts were not yet visible to the core running the ISR. The
> kernel log would get the message "i2c_designware APMC0D0F:00:
> controller timed out" during in-band IPMI SSIF stress tests.
> 
> Add a write barrier before enabling interrupts to assure data written
> by the current core is visible to all cores before the interrupt fires.
> 
> The ARM Barrier Litmus Tests and Cookbook has an example under
> Sending Interrupts and Barriers that matches the usage in this
> driver. That document says a DSB barrier is required.
> 
> Signed-off-by: Jan Bottorff <janb@...amperecomputing.com>
> Reviewed-by: Yann Sionneau <ysionneau@...rayinc.com>
> Tested-by: Yann Sionneau <ysionneau@...rayinc.com>
> ---
>   drivers/i2c/busses/i2c-designware-master.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
Acked-by: Jarkko Nikula <jarkko.nikula@...ux.intel.com>