linux-kernel - Re: [PATCH 2/2] spi: spi-fsl-dspi: Initialize completion before possible interrupt

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Message-ID: <CA+h21hqE3RbD2XTBbcRsMhsO2OaZ65tAaevFOr00p9ezu8O+iA@mail.gmail.com>
Date:   Sun, 14 Jun 2020 16:39:03 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Mark Brown <broonie@...nel.org>,
        Vladimir Oltean <vladimir.oltean@....com>,
        linux-spi <linux-spi@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Wolfram Sang <wsa@...nel.org>, stable@...r.kernel.org
Subject: Re: [PATCH 2/2] spi: spi-fsl-dspi: Initialize completion before
 possible interrupt

On Sun, 14 Jun 2020 at 14:18, Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On Sun, Jun 14, 2020 at 02:14:15PM +0300, Vladimir Oltean wrote:
> > On Sun, 14 Jun 2020 at 13:56, Krzysztof Kozlowski <krzk@...nel.org> wrote:
> > >
> > > If interrupt fires early, the dspi_interrupt() could complete
> > > (dspi->xfer_done) before its initialization happens.
> > >
> > > Fixes: 4f5ee75ea171 ("spi: spi-fsl-dspi: Replace interruptible wait queue with a simple completion")
> > > Cc: <stable@...r.kernel.org>
> > > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> > > ---
> >
> > Why would an interrupt fire before spi_register_controller, therefore
> > before dspi_transfer_one_message could get called?
> > Is this master or slave mode?
>
> I guess practically it won't fire.  It's more of a matter of logical
> order and:
> 1. Someone might fix the CONFIG_DEBUG_SHIRQ_FIXME one day,

And what if CONFIG_DEBUG_SHIRQ_FIXME gets fixed? I uncommented it, and
still no issues. dspi_interrupt checks the status bit of the hw, sees
there's nothing to do, and returns IRQ_NONE.

> 2. The hardware is actually initialized before and someone could attach
>    to SPI bus some weird device.
>

Some weird device that does what?

> Best regards,
> Krzysztof
>

Thanks,
-Vladimir