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

Matthew McClintock
2017-06-14T21:51:32Z

On Wed, Jun 14, 2017 at 2:59 PM, Andy Gross <andy.gross@linaro.org> wrote:
> 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.

Also, this patch presumably fixes an issue seen on Dakota SoCs,
doesn't add or remote the NULL bits.

-M