Re: [PATCH net-next 00/19] net: phy: add support for shared interrupts (part 1)

[Heiner Kallweit]

On 29.10.2020 11:07, Ioana Ciornei wrote:
> From: Ioana Ciornei <ioana.ciornei@xxxxxxx>
> 
> 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.
> 
>>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)

Here I have a concern, bits may be set even if the respective interrupt
source isn't enabled. Therefore we may falsely blame a device to have
triggered the interrupt. irq_status should be masked with the actually
enabled irq source bits.

> 		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.
> 
> This patch set is part 1 and it addresses the changes needed in phylib
> and 7 PHY drivers. The rest can be found on my Github branch here:
> https://github.com/IoanaCiornei/linux/commits/phylib-shared-irq
> 
> I do not have access to most of these PHY's, therefore I Cc-ed the
> latest contributors to the individual PHY drivers in order to have
> access, hopefully, to more regression testing.
> 
> Ioana Ciornei (19):
>   net: phy: export phy_error and phy_trigger_machine
>   net: phy: add a shutdown procedure
>   net: phy: make .ack_interrupt() optional
>   net: phy: at803x: implement generic .handle_interrupt() callback
>   net: phy: at803x: remove the use of .ack_interrupt()
>   net: phy: mscc: use phy_trigger_machine() to notify link change
>   net: phy: mscc: implement generic .handle_interrupt() callback
>   net: phy: mscc: remove the use of .ack_interrupt()
>   net: phy: aquantia: implement generic .handle_interrupt() callback
>   net: phy: aquantia: remove the use of .ack_interrupt()
>   net: phy: broadcom: implement generic .handle_interrupt() callback
>   net: phy: broadcom: remove use of ack_interrupt()
>   net: phy: cicada: implement the generic .handle_interrupt() callback
>   net: phy: cicada: remove the use of .ack_interrupt()
>   net: phy: davicom: implement generic .handle_interrupt() calback
>   net: phy: davicom: remove the use of .ack_interrupt()
>   net: phy: add genphy_handle_interrupt_no_ack()
>   net: phy: realtek: implement generic .handle_interrupt() callback
>   net: phy: realtek: remove the use of .ack_interrupt()
> 
>  drivers/net/phy/aquantia_main.c  |  57 ++++++++++----
>  drivers/net/phy/at803x.c         |  42 ++++++++--
>  drivers/net/phy/bcm-cygnus.c     |   2 +-
>  drivers/net/phy/bcm-phy-lib.c    |  37 ++++++++-
>  drivers/net/phy/bcm-phy-lib.h    |   1 +
>  drivers/net/phy/bcm54140.c       |  39 +++++++---
>  drivers/net/phy/bcm63xx.c        |  20 +++--
>  drivers/net/phy/bcm87xx.c        |  50 ++++++------
>  drivers/net/phy/broadcom.c       |  70 ++++++++++++-----
>  drivers/net/phy/cicada.c         |  35 ++++++++-
>  drivers/net/phy/davicom.c        |  59 ++++++++++----
>  drivers/net/phy/mscc/mscc_main.c |  70 +++++++++--------
>  drivers/net/phy/phy.c            |   6 +-
>  drivers/net/phy/phy_device.c     |  23 +++++-
>  drivers/net/phy/realtek.c        | 128 +++++++++++++++++++++++++++----
>  include/linux/phy.h              |   3 +
>  16 files changed, 484 insertions(+), 158 deletions(-)
> 
> Cc: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
> Cc: Andre Edich <andre.edich@xxxxxxxxxxxxx>
> Cc: Antoine Tenart <atenart@xxxxxxxxxx>
> Cc: Baruch Siach <baruch@xxxxxxxxxx>
> Cc: Christophe Leroy <christophe.leroy@xxxxxx>
> Cc: Dan Murphy <dmurphy@xxxxxx>
> Cc: Divya Koppera <Divya.Koppera@xxxxxxxxxxxxx>
> Cc: Florian Fainelli <f.fainelli@xxxxxxxxx>
> Cc: Hauke Mehrtens <hauke@xxxxxxxxxx>
> Cc: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Cc: Jerome Brunet <jbrunet@xxxxxxxxxxxx>
> Cc: Kavya Sree Kotagiri <kavyasree.kotagiri@xxxxxxxxxxxxx>
> Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Cc: Marco Felsch <m.felsch@xxxxxxxxxxxxxx>
> Cc: Marek Vasut <marex@xxxxxxx>
> Cc: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> Cc: Mathias Kresin <dev@xxxxxxxxx>
> Cc: Maxim Kochetkov <fido_max@xxxxxxxx>
> Cc: Michael Walle <michael@xxxxxxxx>
> Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Cc: Nisar Sayed <Nisar.Sayed@xxxxxxxxxxxxx>
> Cc: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> Cc: Philippe Schenker <philippe.schenker@xxxxxxxxxxx>
> Cc: Willy Liu <willy.liu@xxxxxxxxxxx>
> Cc: Yuiko Oshino <yuiko.oshino@xxxxxxxxxxxxx>
>