The wl1835mod.pdf data sheet says this pretty clearly for WL_IRQ line:

"WLAN SDIO out-of-band interrupt line. Set to rising edge (active high)
by default."

And it seems this interrupt can be optionally configured to use falling
edge too since commit bd763482 ("wl18xx: wlan_irq: support platform
dependent interrupt types").

On omap4, if the wlcore interrupt is configured as level instead of edge,
L4PER will stop doing hardware based idling after ifconfig wlan0 down is
done and the WL_EN line is pulled down.

The symptoms show up with L4PER status registers no longer showing the
IDLEST bits as 2 but as 0 for all the active GPIO banks and for
L4PER_CLKCTRL. Also the l4per_pwrdm RET count stops increasing in
the /sys/kernel/debug/pm_debug/count.

While there is also probably a GPIO related issue that needs to be
still fixed, this change gets us to the point where we can have L4PER
idling.

I'm guessing wlcore was at some point configured to use level interrupts
because of edge handling issues in gpio-omap. However, with the recent
fixes to gpio-omap the edge interrupts seem to be working just fine.

Let's change it for all omap boards with wlcore interrupt set as level.

Cc: Dave Gerlach <d-gerlach@ti.com>
Cc: Eyal Reizer <eyalr@ti.com>
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Kalle Valo <kvalo@codeaurora.org>
Cc: Nishanth Menon <nm@ti.com>
Cc: Tero Kristo <t-kristo@ti.com>
[tony@atomide.com updated comments a bit for gpio issue]
Signed-off-by: Tony Lindgren <tony@atomide.com>