Re: [PATCH v2 1/3] spi: spi-fsl-dspi: Fix external abort on interrupt in exit paths

[Vladimir Oltean]

On Mon, 15 Jun 2020 at 15:35, Mark Brown <broonie@xxxxxxxxxx> 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.

-Vladimir