From: Felix Fietkau <nbd@openwrt.org>
To: Johannes Berg <johannes@sipsolutions.net>,
Janusz Dziedzic <janusz.dziedzic@tieto.com>,
linux-wireless@vger.kernel.org
Subject: Re: [RFC/RFT 1/2] mac80211: Add NEED_ALIGNED4_SKBS hw flag
Date: Thu, 17 Dec 2015 11:09:58 +0100 [thread overview]
Message-ID: <567289F6.2060308@openwrt.org> (raw)
In-Reply-To: <1450346667.8247.23.camel@sipsolutions.net>
On 2015-12-17 11:04, Johannes Berg wrote:
> On Thu, 2015-12-17 at 10:20 +0100, Janusz Dziedzic wrote:
>> HW/driver should set NEED_ALIGNED4_SKBS flag in case require
>> aligned skbs to four-byte boundaries.
>>
>> Before we have to do memmove() in the driver before
>> pass this to HW and memmove() back in tx completion.
>> This patch allow to save CPU and skip such memmoves.
>> For each skb we called memmove(ieee80211_hdrsize()) twice.
>
> IMHO this is pretty awful from a code complexity POV. You also forgot
> to update fast-xmit maximum header length.
>
> Note that we (iwlwifi) also kinda need this, but essentially solve it
> with the DMA engine. Can't ath9k do the same?
I tried that approach a few years ago, but it turned out to make the
hardware unstable, causing random DMA lockups.
- Felix
next prev parent reply other threads:[~2015-12-17 10:10 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-17 9:20 [RFC/RFT 1/2] mac80211: Add NEED_ALIGNED4_SKBS hw flag Janusz Dziedzic
2015-12-17 9:20 ` [RFC/RFT 2/2] ath9k: request aligned skb Janusz Dziedzic
2015-12-21 18:53 ` Souptick Joarder
2015-12-21 22:48 ` Julian Calaby
2015-12-17 9:39 ` [RFC/RFT 1/2] mac80211: Add NEED_ALIGNED4_SKBS hw flag Felix Fietkau
2015-12-17 10:04 ` Johannes Berg
2015-12-17 10:09 ` Felix Fietkau [this message]
2015-12-17 10:12 ` Felix Fietkau
2015-12-18 8:43 ` Janusz Dziedzic
2015-12-17 10:29 ` Johannes Berg
2015-12-17 10:35 ` Felix Fietkau
2015-12-17 10:45 ` Johannes Berg
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