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

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Message-ID: <20200614111829.GA9694@kozik-lap>
Date:   Sun, 14 Jun 2020 13:18:29 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Vladimir Oltean <olteanv@...il.com>
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, 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,
2. The hardware is actually initialized before and someone could attach
   to SPI bus some weird device.

Best regards,
Krzysztof