RE: [EXTERNAL] Re: [PATCH] wlcore: Fix bringing up wlan0 again if powered down briefly

From: "Reizer, Eyal" <eyalr@ti.com>
To: Tony Lindgren <tony@atomide.com>, Ulf Hansson <ulf.hansson@linaro.org>
Cc: 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>
Subject: RE: [EXTERNAL] Re: [PATCH] wlcore: Fix bringing up wlan0 again if powered down briefly
Date: Sun, 23 Dec 2018 07:38:15 +0000	[thread overview]
Message-ID: <c22e2ab61b494ea0852c0f4654fef92d@ti.com> (raw)
In-Reply-To: <20181220231401.GG6707@atomide.com>

> > > > 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
.
> > 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.

> Ricardo, care to play with this too?
> 
Best Regards,
Eyal