Re: [RFC] Fixes for problems with off-channel powersave

[Seth Forshee <seth.forshee@canonical.com>]

On Thu, Jan 17, 2013 at 12:32:43AM +0100, Johannes Berg wrote:
> On Wed, 2013-01-09 at 07:40 -0600, Seth Forshee wrote:
> 
> > > It turns out that fixing problem #1 (i.e. patch 2) probably isn't
> > > necessary with the other changes, as no frames should be sent while
> > > off-channel PS is enabled. Does this still seem like a problem worth
> > > fixing?
> > 
> > This is incorrect. We actually do need patch 2 for some hardware. I
> > forgot that when I was testing with BCM43224 I found that PM gets
> > actively set or cleared based on the device configuration. It's
> > impossible to enable PS at the AP without informing the driver.
> 
> Hm, don't understand. If we're not sending any packets to the AP, why
> does this matter?
> 
> Or are you saying it wants nullfunc frames generated in software, but
> then changes the PM bit in them?

Exactly. At least that's what it looks like to me. I lack detailed
knowledge of how to handle powersave on Broadcom, but I do know that the
PM bit is under the control of the MCTL_HPS field.  Experimentally it
appears that the hardware actively clears PM when this field is 0 and
actively sets it when this field is 1, for all frames including
nullfuncs.

Seth