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

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