Return-path: Received: from mms3.broadcom.com ([216.31.210.19]:1212 "EHLO mms3.broadcom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752068Ab3BMVnc (ORCPT ); Wed, 13 Feb 2013 16:43:32 -0500 Message-ID: <511C08F2.6040008@broadcom.com> (sfid-20130213_224336_772377_156BE529) Date: Wed, 13 Feb 2013 22:43:14 +0100 From: "Arend van Spriel" MIME-Version: 1.0 To: "Seth Forshee" cc: "Johannes Berg" , linux-wireless@vger.kernel.org, "John W. Linville" , "Luis R. Rodriguez" , "Jouni Malinen" , "Vasanthakumar Thiagarajan" , "Senthil Balasubramanian" , "Christian Lamparter" , "Ivo van Doorn" , "Gertjan van Wingerde" , "Helmut Schaa" , "Larry Finger" , "Chaoming Li" , "Wey-Yi Guy" , "Intel Linux Wireless" , "Luciano Coelho" , ath9k-devel@venema.h4ckr.net, brcm80211-dev-list@broadcom.com, users@rt2x00.serialmonkey.com Subject: Re: [PATCH 1/4] mac80211: Convert PS configuration from a binary flag to a set of modes References: <1360184478-31481-1-git-send-email-seth.forshee@canonical.com> <1360184478-31481-2-git-send-email-seth.forshee@canonical.com> <1360767970.8868.24.camel@jlt4.sipsolutions.net> <20130213170445.GC22867@thinkpad-t410> <511BE15B.8090507@broadcom.com> <20130213192519.GD22867@thinkpad-t410> In-Reply-To: <20130213192519.GD22867@thinkpad-t410> Content-Type: text/plain; charset=iso-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 02/13/2013 08:25 PM, Seth Forshee wrote: > On Wed, Feb 13, 2013 at 07:54:19PM +0100, Arend van Spriel wrote: >> On 02/13/2013 06:04 PM, Seth Forshee wrote: >>>> Is all this really worth it? It seems a quick fix for brcmsmac might be >>>>> to always set the powersave bit when IEEE80211_CONF_OFFCHANNEL is >>>>> enabled in the config, and then go implement a real solution like I >>>>> described earlier with powersave being separated out of the core >>>>> mac80211 routines, and actually made possible for multiple interfaces? >>> Using IEEE80211_CONF_OFFCHANNEL won't work. When the nullfunc to enable >>> PS is sent the flag won't be set, as we're still on the operating >>> channel. When we're actually off-channel the value of PM doesn't matter >>> for the types of frames which are being sent. The only quick fix I've >>> found is to watch out for frames with PM set and set the powersave bit >>> while they're being transmitted. >> >> I actually don't see that one fly. The frames are posted on a DMA fifo >> towards the hardware so in the driver we have no clue when that frame is >> being processes/transmitted hence no way of knowing when to write the >> register(s). > > There's a couple of ways of doing it. I had a working patch at one point > but can't seem to find it now, so I'm not sure which way I used. You're > right though that we can't tell when the hardware is actually processing > or transmitting the frame, so in either case MCTL_HPS has to be set > before you put the frame in the tx fifo. > > The first option is that for any frame with PM set, set MCTL_HPS when > mac80211 hands off the frame and clear it once it has finished > transmitting. > > The second option is to look specifically for nullfunc frames and set or > clear MCTL_HPS based on the value of PM. > > Either of these should work fine with the current mac80211 code, but > overall the second one is probably a little safer. So you have verified that the last packet mac80211 sends before going off-channel is the nullfunc frame with PM bit set. I have seen packets coming in our driver during the .flush() callback, but never checked whether the last of those packets is indeed the nullfunc. Gr. AvS