On Fri, Oct 30, 2020 at 10:56:24PM +0100, Heiner Kallweit wrote:

On 29.10.2020 11:07, Ioana Ciornei wrote:

quoted

From: Ioana Ciornei <ioana.ciornei@nxp.com>

This patch set aims to actually add support for shared interrupts in
phylib and not only for multi-PHY devices. While we are at it,
streamline the interrupt handling in phylib.

For a bit of context, at the moment, there are multiple phy_driver ops
that deal with this subject:

- .config_intr() - Enable/disable the interrupt line.

- .ack_interrupt() - Should quiesce any interrupts that may have been
  fired.  It's also used by phylib in conjunction with .config_intr() to
  clear any pending interrupts after the line was disabled, and before
  it is going to be enabled.

- .did_interrupt() - Intended for multi-PHY devices with a shared IRQ
  line and used by phylib to discern which PHY from the package was the
  one that actually fired the interrupt.

- .handle_interrupt() - Completely overrides the default interrupt
  handling logic from phylib. The PHY driver is responsible for checking
  if any interrupt was fired by the respective PHY and choose
  accordingly if it's the one that should trigger the link state machine.

quoted

From my point of view, the interrupt handling in phylib has become

somewhat confusing with all these callbacks that actually read the same
PHY register - the interrupt status.  A more streamlined approach would
be to just move the responsibility to write an interrupt handler to the
driver (as any other device driver does) and make .handle_interrupt()
the only way to deal with interrupts.

Another advantage with this approach would be that phylib would gain
support for shared IRQs between different PHY (not just multi-PHY
devices), something which at the moment would require extending every
PHY driver anyway in order to implement their .did_interrupt() callback
and duplicate the same logic as in .ack_interrupt(). The disadvantage
of making .did_interrupt() mandatory would be that we are slightly
changing the semantics of the phylib API and that would increase
confusion instead of reducing it.

What I am proposing is the following:

- As a first step, make the .ack_interrupt() callback optional so that
  we do not break any PHY driver amid the transition.

- Every PHY driver gains a .handle_interrupt() implementation that, for
  the most part, would look like below:

	irq_status = phy_read(phydev, INTR_STATUS);
	if (irq_status < 0) {
		phy_error(phydev);
		return IRQ_NONE;
	}

	if (irq_status == 0)
		return IRQ_NONE;

	phy_trigger_machine(phydev);

	return IRQ_HANDLED;

- Remove each PHY driver's implementation of the .ack_interrupt() by
  actually taking care of quiescing any pending interrupts before
  enabling/after disabling the interrupt line.

- Finally, after all drivers have been ported, remove the
  .ack_interrupt() and .did_interrupt() callbacks from phy_driver.

Looks good to me. The current interrupt support in phylib basically
just covers the link change interrupt and we need more flexibility.

And even in the current limited use case we face smaller issues.
One reason is that INTR_STATUS typically is self-clearing on read.
phylib has to deal with the case that did_interrupt may or may not
have read INTR_STATUS already.

I'd just like to avoid the term "shared interrupt", because it has
a well-defined meaning. Our major concern isn't shared interrupts
but support for multiple interrupt sources (in addition to
link change) in a PHY.

I am not going to address this part, Vladimir did a good job in the
following emails describing exactly the problem that I am trying to fix
- shared interrupts even between PHYs which are not in the same package
or even the same type of device.

WRT implementing a shutdown hook another use case was mentioned
recently: https://lkml.org/lkml/2020/9/30/451
But that's not really relevant here and just fyi.

I missed this thread. Thanks for the link!

Ioana