On 24/09/20 8:27 am, Heiner Kallweit wrote:

On 04.09.2020 02:28, Chris Packham wrote:

quoted

The SPIE register contains counts for the TX FIFO so any time the irq
handler was invoked we would attempt to process the RX/TX fifos. Use the
SPIM value to mask the events so that we only process interrupts that
were expected.

This was a latent issue exposed by commit 3282a3da25bd ("powerpc/64:
Implement soft interrupt replay in C").

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Cc: stable@vger.kernel.org
---

Notes:
     I've tested this on a T2080RDB and a custom board using the T2081 SoC. With
     this change I don't see any spurious instances of the "Transfer done but
     SPIE_DON isn't set!" or "Transfer done but rx/tx fifo's aren't empty!" messages
     and the updates to spi flash are successful.
     
     I think this should go into the stable trees that contain 3282a3da25bd but I
     haven't added a Fixes: tag because I think 3282a3da25bd exposed the issue as
     opposed to causing it.

  drivers/spi/spi-fsl-espi.c | 5 +++--
  1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 7e7c92cafdbb..cb120b68c0e2 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/drivers/spi/spi-fsl-espi.c

@@ -574,13 +574,14 @@ static void fsl_espi_cpu_irq(struct fsl_espi *espi, u32 events)
  static irqreturn_t fsl_espi_irq(s32 irq, void *context_data)
  {
  	struct fsl_espi *espi = context_data;
-	u32 events;
+	u32 events, mask;
  
  	spin_lock(&espi->lock);
  
  	/* Get interrupt events(tx/rx) */
  	events = fsl_espi_read_reg(espi, ESPI_SPIE);
-	if (!events) {
+	mask = fsl_espi_read_reg(espi, ESPI_SPIM);
+	if (!(events & mask)) {
  		spin_unlock(&espi->lock);
  		return IRQ_NONE;

Sorry, I was on vacation and therefore couldn't comment earlier.
I'm fine with the change, just one thing could be improved IMO.
If we skip an unneeded interrupt now, then returning IRQ_NONE
causes reporting this interrupt as spurious. This isn't too nice
as spurious interrupts typically are seen as a problem indicator.
Therefore returning IRQ_HANDLED should be more appropriate.
This would just require a comment in the code explaining why we
do this, and why it can happen that we receive interrupts
we're not interested in.

I'd be happy to send a follow-up to change IRQ_NONE to IRQ_HANDLED. I 
don't think the old code could have ever hit the IRQ_NONE (because event 
will always be non-zero) so it won't really be a change in behaviour. 
With the patch (that is now in spi/for-next) so far I do see a low 
number of spurious interrupts on the test setup where previously I would 
have seen failure to talk to the spi-flash.