netdev - [PATCH 0/4] net: dsa: mv88e6xxx: novice fixes and irq handling

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Date:   Mon, 19 Mar 2018 11:05:19 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     kernel@...gutronix.de, Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org,
        Gregory CLEMENT <gregory.clement@...e-electrons.com>
Subject: [PATCH 0/4] net: dsa: mv88e6xxx: novice fixes and irq handling

Hello,

this is a set of patches I created while I tried to understand how DSA
works. I don't claim I already got there and so the first 3 fixes are
trivial only.

I tried to make the switch on the espressobin SBC use the interrupt line
and needed the fourth patch to make this work. Given I don't have access
to the documentation of the Marvell switch, the patch is probably not
correct though (and so doesn't have a S-o-b).

When I first added the irq as:

	interrupt-parent = <&gpiosb>;
	interrupts = <23 IRQ_TYPE_LEVEL_LOW>;

to the switch of the espressobin's dtb, the irq couldn't be used. The
reason is the interaction of several things:

 - On the first try to probe the switch, the driver did:

	irq = of_irq_get(np, 0);
	request_threaded_irq(irq, NULL, func, IRQF_ONESHOT | IRQF_TRIGGER_FALLING, ...);

   and then later aborted with -EPROBE_DEFER because another resource
   wasn't available yet. This correctly undid the request_threaded_irq
   above using free_irq.

 - When the probe routine was entered again, the call to of_irq_get(np, 0)
   failed becauce the irq code remembered that the irq was requested
   using edge triggered logic with:

	irq: type mismatch, failed to map hwirq-23 for gpio!

   (kernel/irq/irqdomain.c, line 801)

Any of the following changes would make the problem disappear:

 - use IRQ_TYPE_EDGE_FALLING in the device tree;
 - drop IRQF_TRIGGER_FALLING from the driver's use of
   request_threaded_irq() (I think, see below); and
 - make the irq code forget the trigger type when the last action is
   removed

I think both the second and the third should be done.

For the third, after a quick look into kernel/irq I didn't find a
suitable place where to do that and so it would be great to get some
feedback from Marc or Thomas here.

Regarding the first one: Is the irq of the switch really edge sensitive?
I didn't see the line reset to 1 after an irq was triggered. (And again,
I don't have access on the documentation of the switch.) When I tested
the second change however the driver still failed because the
gpio controller doesn't support level sensitive irqs. :-|

Looking forward to your comments
Uwe Kleine-Köníg

Uwe Kleine-König (4):
  net: dsa: mv88e6xxx: Fix name of switch 88E6141
  net: dsa: mv88e6xxx: Fix typo in a comment
  net: dsa: mv88e6xxx: Fix interrupt name for g2 irq
  net: dsa: mv88e6xxx: Guess number of g1 irqs

 drivers/net/dsa/mv88e6xxx/chip.c    | 6 ++++--
 drivers/net/dsa/mv88e6xxx/global2.c | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

-- 
2.16.2