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Subject: Re: [PATCH v8 2/6] mt76: mt76x02: split beaconing
To:     Stanislaw Gruszka <sgruszka@redhat.com>,
        Markus Theil <markus.theil@tu-ilmenau.de>
Cc:     linux-wireless@vger.kernel.org, lorenzo.bianconi@redhat.com
References: <20191121180001.22451-1-markus.theil@tu-ilmenau.de>
 <20191121180001.22451-3-markus.theil@tu-ilmenau.de>
 <20191125130014.GB28102@redhat.com>
 <ec1b9623-2aa1-27c7-abcd-2b39e0d25a0c@tu-ilmenau.de>
 <20191125165932.GB14273@redhat.com>
From:   Felix Fietkau <nbd@nbd.name>
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Message-ID: <40c52ae5-85d8-8a65-2b4b-1a52bf1b73ab@nbd.name>
Date:   Mon, 25 Nov 2019 18:12:56 +0100
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On 2019-11-25 17:59, Stanislaw Gruszka wrote:
> On Mon, Nov 25, 2019 at 03:07:59PM +0100, Markus Theil wrote:
>> On 11/25/19 2:00 PM, Stanislaw Gruszka wrote:
>> > On Thu, Nov 21, 2019 at 06:59:57PM +0100, Markus Theil wrote:
>> >> +void mt76x02_mac_set_beacon_finish(struct mt76x02_dev *dev)
>> >> +{
>> >> +	mt76_wr(dev, MT_BCN_BYPASS_MASK,
>> >> +		0xff00 | ~bitrev8(dev->beacon_data_mask));
>> > Since you arrange beacon slots continues starting from 0
>> > (i.e. 0,1,2 instead of "random" vif_idx values like 0,4,6),
>> > I think it would make sense to keep
>> > MT_MAC_BSSID_DW1_MBEACON_N = bcn_idx - 1 and set mask unchanged.
>> >
>> > But no strong opinion here, code with bitrev8 looks fine too.
>> I'd like to keep the bitrev8 code, as it saves a copy over usb for usb
>> devices, if MT_MAC_BSSID_DW_BEACON_N is kept constant.
>> bitrev8 should be a rather cheap operation compared to a copy over some
>> form of bus.
> 
> This make sense. I tested the code on MT7630E and after adding missed
> write_txwi function, it works fine. So I think bitrev8 code is ok.
I find the use of bitrev8/ffz a bit convoluted. If I understand the code
right, wouldn't it be equivalent to keeping beacon_data_count instead of
beacon_data_mask and doing:
mt76_wr(dev, MT_BCN_BYPASS_MASK,
	0xffff & ~((1 << dev->beacon_data_count) - 1));
If so, I would strongly prefer the beacon_data_count variant. It's also
cheaper to calculate, though that probably doesn't matter, since it's
not really a hot path.

- Felix