linux-kernel - Re: [PATCH] spi: dw: use "smp_mb()" to avoid sending spi data error

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Message-ID: <fca15988-22eb-2ba9-037e-7f7f51221fe4@hisilicon.com>
Date:   Fri, 3 Jan 2020 09:34:33 +0800
From:   kongxinwei <kong.kongxinwei@...ilicon.com>
To:     Mark Brown <broonie@...nel.org>
CC:     <linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, fengsheng <fengsheng5@...wei.com>,
        kXinwei Kong <kong.kongxinwei@...ilicon.com>
Subject: Re: [PATCH] spi: dw: use "smp_mb()" to avoid sending spi data error



On 2020/1/3 9:04, Mark Brown wrote:
> On Sat, Dec 28, 2019 at 04:31:53PM +0800, kongxinwei wrote:
> 
>>> I'd be much more comfortable here if I understood what this was
>>> supposed to be syncing - what exactly gets flushed here and why
>>> is a memory barrier enough to ensure it's synced?  A comment in
>>> the code would be especially good so anyone modifying the code
>>> understands this in future.
> 
>> Because of out-of-order execution about some CPU architecture,
>> In this debug stage we find Completing spi interrupt enable ->
>> prodrucing TXEI interrupt -> running "interrupt_transfer" function
>> will prior to set "dw->rx and dws->rx_end" data, so it will result
>> in SPI sending error
> 
> Could you update the commit message to say that, and ideally also
> add a comment saying something like "Ensure dw->rx and dw->rx_end
> are visible" please?
> 
OK, i WILL update it.