Re: [PATCH 11/18] spi: qup: properly detect extra interrupts

Andy Gross
2017-06-14T19:59:58Z

On Wed, Jun 14, 2017 at 12:57:25PM +0530, Sricharan R wrote:
> Hi Varada,
>
> On 6/14/2017 11:22 AM, Varadarajan Narayanan wrote:
> > It's possible for a SPI transaction to complete and get another
> > interrupt and have it processed on the same spi_transfer before the
> > transfer_one can set it to NULL.
> >
> > This masks unexpected interrupts, so let's set the spi_transfer to
> > NULL in the interrupt once the transaction is done. So we can
> > properly detect these bad interrupts and print warning messages.
> >
> > Signed-off-by: Matthew McClintock <mmcclint@codeaurora.org>
> > Signed-off-by: Varadarajan Narayanan <varada@codeaurora.org>
> > ---
> > drivers/spi/spi-qup.c | 20 +++++++++++---------
> > 1 file changed, 11 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/spi/spi-qup.c b/drivers/spi/spi-qup.c
> > index bd53e82..1a2a9d9 100644
> > --- a/drivers/spi/spi-qup.c
> > +++ b/drivers/spi/spi-qup.c
> > @@ -496,13 +496,13 @@ static irqreturn_t spi_qup_qup_irq(int irq, void *dev_id)
> > struct spi_qup *controller = dev_id;
> > struct spi_transfer *xfer;
> > u32 opflags, qup_err, spi_err;
> > - unsigned long flags;
> > int error = 0;
> > + bool done = 0;
> >
> > - spin_lock_irqsave(&controller->lock, flags);
> > + spin_lock(&controller->lock);
> > xfer = controller->xfer;
> > controller->xfer = NULL;
> > - spin_unlock_irqrestore(&controller->lock, flags);
> > + spin_unlock(&controller->lock);
>
> Why change the locking here ?
>
> >
> > qup_err = readl_relaxed(controller->base + QUP_ERROR_FLAGS);
> > spi_err = readl_relaxed(controller->base + SPI_ERROR_FLAGS);
> > @@ -556,16 +556,19 @@ static irqreturn_t spi_qup_qup_irq(int irq, void *dev_id)
> > spi_qup_write(controller, xfer);
> > }
> >
> > - spin_lock_irqsave(&controller->lock, flags);
> > - controller->error = error;
> > - controller->xfer = xfer;
> > - spin_unlock_irqrestore(&controller->lock, flags);
> > -
> > /* re-read opflags as flags may have changed due to actions above */
> > opflags = readl_relaxed(controller->base + QUP_OPERATIONAL);
> >
> > if ((controller->rx_bytes == xfer->len &&
> > (opflags & QUP_OP_MAX_INPUT_DONE_FLAG)) || error)
> > + done = true;
> > +
> > + spin_lock(&controller->lock);
> > + controller->error = error;
> > + controller->xfer = done ? NULL : xfer;
> > + spin_unlock(&controller->lock);
> > +
> > + if (done)
> > complete(&controller->done);
> >
> Its not clear, why the driver is setting the controller->xfer = NULL
> and restoring it inside the irq. This patch seems to fix things on
> top of that.

I think the original intent was to make sure that the irqhandler knew that there
was no outstanding transaction. This begs the question of why that would ever
be necessary. I think it would suffice to rework all of that to remove that
behavior and perhaps enable/disable the irq as we need to during transactions.

I've never been a fan of the controller->xfer being set to NULL.

Regards,

Andy