Hi,

On Wed, Aug 26, 2020 at 7:51 AM Kalle Valo [off-list ref] wrote:

Douglas Anderson [off-list ref] wrote:

quoted

If we have a per CE (Copy Engine) IRQ then we have no summary
register.  Right now the code generates a summary register by
iterating over all copy engines and seeing if they have an interrupt
pending.

This has a problem.  Specifically if _none_ if the Copy Engines have
an interrupt pending then they might go into low power mode and
reading from their address space will cause a full system crash.  This
was seen to happen when two interrupts went off at nearly the same
time.  Both were handled by a single call of ath10k_snoc_napi_poll()
but, because there were two interrupts handled and thus two calls to
napi_schedule() there was still a second call to
ath10k_snoc_napi_poll() which ran with no interrupts pending.

Instead of iterating over all the copy engines, let's just keep track
of the IRQs that fire.  Then we can effectively generate our own
summary without ever needing to read the Copy Engines.

Tested-on: WCN3990 SNOC WLAN.HL.3.2.2-00490-QCAHLSWMTPL-1

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Rakesh Pillai <redacted>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <redacted>

My main concern of this patch is that there's no info how it works on other
hardware families. For example, QCA9984 is very different from WCN3990. The
best would be if someone can provide a Tested-on tags for other hardware (even
some of them).

I simply don't have access to any other Atheros hardware.  Hopefully
others on this thread do, though?  ...but, if nothing else, I believe
code inspection shows that the only places that are affected by the
changes here are:

* Wifi devices that use "snoc.c".  The only compatible string listed
in "snoc.c" is wcn3990.

* Wifi devices that set "per_ce_irq" to true.  The only place in the
table where this is set to true is wcn3990.

While it is certainly possible that I messed up and somehow affected
other WiFi devices, the common bits of code in "ce.c" and "ce.h" are
fairly easy to validate so hopefully they look OK?

-Doug