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Date:   Mon, 15 Jun 2020 15:10:12 +0200
From:   Krzysztof Kozlowski <krzk@kernel.org>
To:     Vladimir Oltean <olteanv@gmail.com>
Cc:     Mark Brown <broonie@kernel.org>,
        Marc Kleine-Budde <mkl@pengutronix.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vladimir Oltean <vladimir.oltean@nxp.com>,
        linux-spi <linux-spi@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Wolfram Sang <wsa@kernel.org>, stable@vger.kernel.org,
        Pengutronix Kernel Team <kernel@pengutronix.de>
Subject: Re: [PATCH v2 1/3] spi: spi-fsl-dspi: Fix external abort on
 interrupt in exit paths
Message-ID: <20200615131012.GB2634@kozik-lap>
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On Mon, Jun 15, 2020 at 03:56:01PM +0300, Vladimir Oltean wrote:
> On Mon, 15 Jun 2020 at 15:35, Mark Brown <broonie@kernel.org> wrote:
> >
> 
> >
> > Indeed.  The upshot of all this is that the interrupt needs to be freed
> > not disabled before the clocks are disabled, or some other mechanism
> > needs to be used to ensure that the interrupt handler won't attempt to
> > access the hardware when it shouldn't.  As Vladimir says there are
> > serious issues using devm for interrupt handlers (or anything else that
> > might cause code to be run) due to problems like this.
> 
> And the down-shot is that whatever is done in dspi_remove (free_irq)
> also needs to be done in dspi_suspend, but with extra care in
> dspi_resume not only to request the irq again, but also to flush the
> module's FIFOs and clear interrupts, because there might have been
> nasty stuff uncaught during sleep:
> 
>     regmap_update_bits(dspi->regmap, SPI_MCR,
>                SPI_MCR_CLR_TXF | SPI_MCR_CLR_RXF,
>                SPI_MCR_CLR_TXF | SPI_MCR_CLR_RXF);
>     regmap_write(dspi->regmap, SPI_SR, SPI_SR_CLEAR);
> 
> So it's pretty messy.

It is a slightly different bug which so this patch should have a follow
up.

Best regards,
Krzysztof