On Mon, Oct 04, 2021 at 09:36:37AM -0700, Florian Fainelli wrote:

On 10/4/21 9:31 AM, Mark Brown wrote:

quoted

an issue, someone could press a button or whatever.  Frankly for SPI the
quiescing part doesn't seem like logic that should be implemented in
drivers, it's a subsystem level thing since there's nothing driver
specific about it.

Surely the SPI subsystem can help avoid queuing new transfers towards
the SPI controller while the controller can shut down the resources that
only it knows about.

Yes, that's what I was saying.

quoted

In the case of this specific driver I'm still not clear that the best
thing isn't just to delete the shutdown callback and let any ongoing
transfers complete, though I guess there'd be issues in kexec cases with
long enough tansfers.

No please don't, I should have arguably justified the reasons why
better, but the main reason is that one of the platforms on which this
driver is used has received extensive power management analysis and
changes, and shutting down every bit of hardware, including something as
small as a SPI controller, and its clock (and its PLL) helped meet
stringent power targets.

OK, so it's similar to a lot of the other embedded cases where it's for
a power down that doesn't cut as much power as would be desirable -
that's reasonable.  Like you say you didn't mention it at all in the
changelog.  Ideally the hardware would just cut all power to the SoC in
shutdown but then IIRC those boards don't have a PMIC so...  

TBH, I still wonder why we have .shutdown() and we simply don't use
.remove() which would reduce the amount of work that people have to do
validate that the hardware is put in a low power state and would also
reduce the amount of burden on the various subsystems.

Yeah, it does seem a bit odd - I'd figured it was for speed reasons.