Re: [PATCH 11/12] PM, libnvdimm: Add syscore_quiesced() callback for firmware activation

[Rafael J. Wysocki]

On Fri, Jun 26, 2020 at 2:07 AM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> The runtime firmware activation capability of Intel NVDIMM devices
> requires memory transactions to be disabled for 100s of microseconds.
> This timeout is large enough to cause in-flight DMA to fail and other
> application detectable timeouts. Arrange for firmware activation to be
> executed while the system is "quiesced" all suspend operations have
> completed successfully.
>
> Note that the placement of syscore_quiesced() before
> suspend_disable_secondary_cpus() and the "TEST_PLATFORM" early exit in
> suspend_enter():
>
>         if (suspend_test(TEST_PLATFORM))
>                 goto Platform_wake;
>
> ...is a deliberate tradeoff. suspend_disable_secondary_cpus() causes
> violence to drivers with many interrupts allocated (server-class network
> adapters for example). So, allow for triggering firmware-activation
> without requiring all irq vectors to be routed (oversubscribed) to a
> single CPU.

So while the other patches in the series look good to me, this is kind
of questionable for reasons described in my reply to the intro
message.

Cheers!