On Sun, Jun 14, 2020 at 04:43:28PM +0300, Vladimir Oltean wrote:
> On Sun, 14 Jun 2020 at 16:39, Vladimir Oltean <olteanv@xxxxxxxxx> wrote:
> >
> > On Sun, 14 Jun 2020 at 14:18, Krzysztof Kozlowski <krzk@xxxxxxxxxx> 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@xxxxxxxxxx> 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")
>
> Also please note that this patch merely replaced an
> init_waitqueue_head with init_completion. But the "bug" (if we can
> call it that) originates from even before.
Yeah, I know, the Fixes is not accurate. Backport to earlier kernels
would be manual so I am not sure if accurate Fixes matter.
>
> > > > > Cc: <stable@xxxxxxxxxxxxxxx>
> > > > > Signed-off-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
> > > > > ---
> > > >
> > > > 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.
Indeed, still the logical way of initializing is to do it before any
possible use.
> >
> > > 2. The hardware is actually initialized before and someone could attach
> > > to SPI bus some weird device.
> > >
> >
> > Some weird device that does what?
You never know what people will connect to a SoM :).
Wolfram made actually much better point - bootloaders are known to
initialize some things and leaving them in whatever state, assuming that
Linux kernel will redo any initialization properly.
Best regards,
Krzysztof
