Re: [PATCH] net: phy: Move interrupt check from phy_check to phy_interrupt

Thanks for the feedback, Sergei.

On Thu, Mar 08, 2018 at 10:41:04PM +0300, Sergei Shtylyov wrote:

Hello!

On 03/08/2018 01:50 AM, Brad Mouring wrote:

quoted

If multiple phys share the same interrupt (e.g. a multi-phy chip),
the first device registered is the only one checked as phy_interrupt
will always return IRQ_HANDLED if the first phydev is not halted.
Move the interrupt check into phy_interrupt and, if it was not this
phydev, return IRQ_NONE to allow other devices on this irq a chance
to check if it was their interrupt.

   Hm, looking at kernel/irq/handle.c, all registered IRQ handlers are always
called regardless of their results. Care to explain?

In the phy interrupt handler case, the phy_interrupt function is
registered as the threaded secondary, and irq_default_primary_handler
is being used as the primary (which will turn around and wake the
threaded handler). It seems that we wake the thread_fns in order, and
the first to report back HANDLED stops us from waking the next.

quoted

Signed-off-by: Brad Mouring <redacted>
---
 drivers/net/phy/phy.c | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index e3e29c2b028b..ff1aa815568f 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c

@@ -632,6 +632,12 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
 	if (PHY_HALTED == phydev->state)
 		return IRQ_NONE;		/* It can't be ours.  */
 
+	if (phy_interrupt_is_valid(phydev)) {

  Always true in this context, no?

Yes, already noted.

quoted

+		if (phydev->drv->did_interrupt &&
+			!phydev->drv->did_interrupt(phydev))

   I don't think we can do this in the interrupt context as this function *will*
read from MDIO... I think that was the reason why IRQ handling is done in the
thread context... 

phy_interrupt is the thread_fn here. We're not in interrupt context.

quoted

+			return IRQ_NONE;
+	}
+
 	phy_change(phydev);
 
 	return IRQ_HANDLED;

[...]

MBR, Sergei

Thanks,
Brad