net: phy: mxl-gpy: add MDINT workaround
At least the GPY215B and GPY215C has a bug where it is still driving the interrupt line (MDINT) even after the interrupt status register is read and its bits are cleared. This will cause an interrupt storm. Although the MDINT is multiplexed with a GPIO pin and theoretically we could switch the pinmux to GPIO input mode, this isn't possible because the access to this register will stall exactly as long as the interrupt line is asserted. We exploit this very fact and just read a random internal register in our interrupt handler. This way, it will be delayed until the external interrupt line is released and an interrupt storm is avoided. The internal register access via the mailbox was deduced by looking at the downstream PHY API because the datasheet doesn't mention any of this. Fixes: 7d901a1e ("net: phy: add Maxlinear GPY115/21x/24x driver") Signed-off-by:Michael Walle <michael@walle.cc> Reviewed-by: