Re: [PATCH] wlcore: sdio: Fixup power on/off sequence

[Ulf Hansson <ulf.hansson@linaro.org>]

On Tue, 15 Jan 2019 at 19:55, Tony Lindgren <tony@atomide.com> wrote:
>
> Hi,
>
> * Ulf Hansson <ulf.hansson@linaro.org> [190115 15:04]:
> > During "wlan-up", we are programming the FW into the WiFi-chip. However,
> > re-programming the FW doesn't work, unless a power cycle of the WiFi-chip
> > is made in-between the programmings.
> >
> > To conform to this requirement and to fix the regression in a simple way,
> > let's start by allowing that the SDIO card (WiFi-chip) may stay powered on
> > (runtime resumed) when wl12xx_sdio_power_off() returns. The intent with the
> > current code is to treat this scenario as an error, but unfortunate this
> > doesn't work as expected, so let's fix this.
> >
> > The other part is to guarantee that a power cycle of the SDIO card has been
> > completed when wl12xx_sdio_power_on() returns, as to allow the FW
> > programming to succeed. However, relying solely on runtime PM to deal with
> > this isn't sufficient. For example, userspace may prevent runtime suspend
> > via sysfs for the device that represents the SDIO card, leading to that the
> > mmc core also keeps it powered on. For this reason, let's instead do a
> > brute force power cycle in wl12xx_sdio_power_on().
>
> Thanks this looks good.. But looks like udelay 20000
> is needed with:

Thanks for testing!

>
> # while [ 1 ]; do ifconfig wlan0 down; usleep 20000; \
>   ifconfig wlan0 up; done
>
> Otherwise I get the following on warning pandaboard-es:
>
> WARNING: CPU: 0 PID: 1770 at drivers/bus/omap_l3_noc.c:147
> l3_interrupt_handler+0x2f8/0x388
> 44000000.ocp:L3 Custom Error: MASTER MPU TARGET L4PER2 (Read):
> Data Access in User mode during Functional access
>
> Meaning that we access registers while not clocked
> somewhere. I think that warning is different from the
> earlier errors though :) And we could add a msleep(50)
> to the end to mostly avoid it until we have a better
> fix available?

Well, that would paper over the problem, let's see if we can avoid it.

I realized that I have not invoked mmc_hw_reset() with the sdio host
claimed. This could be the reason and is fixed in a v2, please try and
see if that solves the "new" problem. If id doesn't, you could also
convert the pm_runtime_put() to a pm_runtime_put_sync() in
wl12xx_sdio_power_off() and see if that makes a difference.

Kind regards
Uffe