linux-kernel - Re: [PATCH v2 2/2] spi: loongson: add bus driver for the loongson spi controller

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Date:   Tue, 21 Mar 2023 12:08:46 +0000
From:   Mark Brown <broonie@...nel.org>
To:     zhuyinbo <zhuyinbo@...ngson.cn>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jianmin Lv <lvjianmin@...ngson.cn>,
        wanghongliang@...ngson.cn, Liu Peibao <liupeibao@...ngson.cn>,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH v2 2/2] spi: loongson: add bus driver for the loongson
 spi controller

On Tue, Mar 21, 2023 at 10:54:32AM +0800, zhuyinbo wrote:
> 在 2023/3/20 下午8:52, Mark Brown 写道:

> > No, that doesn't help if setup() reconfigures the controller while it's
> > doing a transfer.  The issue is that the controller might be put into
> > the wrong mode or run at the wrong speed.

> sorry, I don't got that why cpu still can call setup's critical region when
> cpu call transfer_one to  transfer spi data.

> when I added a spin_lock for setup and transfer_one then setup and
> transfer_one's critical region cann't be called

> simultaneously as I know, because the their lock was same lock.

Think what happens if the two SPI devices have different configurations
- for example, a different SPI mode.  The register state won't be
corrupted but the devices will still end up seeing misconfigured SPI
transfers.

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