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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Fri, 28 Dec 2018 10:48:23 +0100
Message-ID: <CAPDyKFrk8Fx_XywPjhW3CTV9ri0LDovUuhE8=15Zew0_gMgebg@mail.gmail.com>
Subject: Re: [EXTERNAL] Re: [PATCH] wlcore: Fix bringing up wlan0 again if
 powered down briefly
To:     "Reizer, Eyal" <eyalr@ti.com>
Cc:     Tony Lindgren <tony@atomide.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        KISHON VIJAY ABRAHAM <kishon@ti.com>,
        "Mishol, Guy" <guym@ti.com>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        linux-omap <linux-omap@vger.kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>,
        John Stultz <john.stultz@linaro.org>,
        Ricardo Salveti <rsalveti@rsalveti.net>
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Sender: linux-wireless-owner@vger.kernel.org
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On Sun, 23 Dec 2018 at 08:38, Reizer, Eyal <eyalr@ti.com> wrote:
>
> > > > > Instead, it looks like what you need, is a way to keep track of
> > > > > whether the SDIO card, became power cycled or if it stayed powered
> > on,
> > > > > when "ifconfig wlan0 up" is done. In case of a power cycle, you need
> > > > > to re-program the firmware, right?
> > > >
> > > > Yeah mostly. But we also need to ensure things do get powered down
> > > > properly after ifconfig wlan0 down :) IMO after ifconfig wlan0 down
> > > > returns, there should be no waiting needed.
> > > >
> > > > > Would it be possible to re-program the firmware, even if the SDIO card
> > > > > stayed powered-on?
> > > >
> > > > That might help for some cases, but the problem of how to ensure the
> > > > card is powered down after ifconfig wlan0 down returns still exists.
> > >
> > > Well, does the SDIO card really have to be powered down before
> > > "ifconfig wlan0 down" returns? If so, why?
> >
> > Good question. Eyal, any comments what should happen here from
> > the wlcore hardware point of view?
> >
>
> You are ok as long as the wlan_enable pin Does go down for a sufficient amount of time
> turning the wl18xx device off.
> The firmware can only be downloaded once after power on.
> In between down/up you have to make sure the wlan_enable is fully going through on->off->on
> and the wl18xx device is fully reset.
> On power on the firmware is loaded by the driver and this will fail in case the reset didn't happen

This clearly answers one of my question, in regards to re-programming
the FW, thanks!

However, I am still lacking an answer to if there is hard requirement
to actually power off the SDIO card at "down". So far, the indications
I have got, gives that answer "yes". Can you or anybody else confirm
that?

> .
> > > An option would be to call pm_runtime_get_sync() at "ifconfig wlan0
> > > up" (I assume you already do that) and then re-program the firmware,
> > > even if the card hasn't been power cycled. Wouldn't that work?
> >
> No, this wouldn't work in case the wlan_enable pin didn't reset the chip as part of the
> "ifconfig wlan0 down" Command.
>
> > Ricardo, care to test and see if the problem comes back if you
> > keep PM runtime enabled?
> >
> > > Or perhaps this is the problem you are encountering, that the FW can't
> > > be reprogrammed, unless the card has been power cycled? You can easily
> > > test that, by simply bumping the runtime usage count for the card
> > > device via sysfs, before doing the "ifconfig wlan0 up/down" thingy.
> >
>
> Correct. The firmware can't be reprogrammed , unless the card has been power cycled.

Again, thanks for clarifying this.

[...]

Kind regards
Uffe