linux-kernel - Re: [PATCH] mt76: mt7615: add support for per-chain signal strength reporting

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Date:   Mon, 10 Jun 2019 15:12:09 +0800
From:   Ryder Lee <ryder.lee@...iatek.com>
To:     Sebastian Gottschall <s.gottschall@...media-net.de>
CC:     Sean Wang <sean.wang@...iatek.com>,
        Chih-Min Chen <chih-min.Chen@...iatek.com>,
        YF Luo <yf.luo@...iatek.com>, <linux-wireless@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        Yiwei Chung <yiwei.chung@...iatek.com>,
        <linux-mediatek@...ts.infradead.org>, Roy Luo <royluo@...gle.com>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        "Felix Fietkau" <nbd@....name>
Subject: Re: [PATCH] mt76: mt7615: add support for per-chain signal strength
 reporting

On Mon, 2019-06-10 at 06:47 +0200, Sebastian Gottschall wrote:
> okay. curious is, that my variant works with sane results too.
> i will test your variant and check the results
> 
> Sebastian

Please don't top post as it's hard to track the thread.

More specifically, IBRSSI is obtained from packet's L-STF portion and
MTK HW PD (packet detection) will take it as a reference. (with
variation more or less)

As for RCPI which is calculated from packet's data portion. The other
MTK chipsets may use IBRSSI as their baseband couldn't report RCPI.

Ryder

> Am 10.06.2019 um 06:22 schrieb Ryder Lee:
> > On Mon, 2019-06-10 at 10:09 +0800, Ryder Lee wrote:
> >> On Sun, 2019-06-09 at 16:44 +0200, Sebastian Gottschall wrote:
> >>> according to my findings
> >>>
> >>> MT_RXV4_RCPI1 is part of rx descriptor 4 and not 3
> >>> so it must be rxdg4 = rxd[4] etc.
> >> RXV start from 1 in the code.
> >>
> >> That is: RXV1 <-> rxdg0, RXV2 <-> rxdg1 ...so RXV4 <-> rxdg3
> >>
> >>> however rxdg3 contains MT_RXV3_IB_RSSIRX which can be used for signal calculation.
> >>> i already wrote a similar code for this driver which i sended to felix a long time ago.
> >>> my variant looks like
> >>>                   status->signal = (FIELD_GET(MT_RXV3_IB_RSSIRX, rxdg3) - 220) / 2;
> >>>                   status->chain_signal[0] = (FIELD_GET(MT_RXV4_RCPI0, rxdg4) - 220) / 2;
> >>>                   status->chain_signal[1] = (FIELD_GET(MT_RXV4_RCPI1, rxdg4) - 220) / 2;
> >>>                   status->chain_signal[2] = (FIELD_GET(MT_RXV4_RCPI2, rxdg4) - 220) / 2;
> >>>                   status->chain_signal[3] = (FIELD_GET(MT_RXV4_RCPI3, rxdg4) - 220) / 2;
> > mt7615 actually doesn't use in-band RSSI for signal calculation, but it
> > occurs to me that i should modify the code to compare per-chain's
> > signal. Something like this:
> >
> > 		status->chain_signal[0] = to_rssi(MT_RXV4_RCPI0, rxdg3);
> > 		status->chain_signal[1] = to_rssi(MT_RXV4_RCPI1, rxdg3);
> > 		status->chain_signal[2] = to_rssi(MT_RXV4_RCPI2, rxdg3);
> > 		status->chain_signal[3] = to_rssi(MT_RXV4_RCPI3, rxdg3);
> > 		status->signal = status->chain_signal[0];
> >
> > 		switch (status->chains) {
> > 		case 0xf:
> > 			status->signal = max(status->signal,
> > 					     status->chain_signal[3]);
> > 		case 0x7:
> > 			status->signal = max(status->signal,
> > 					     status->chain_signal[2]);
> > 		case 0x3:
> > 			status->signal = max(status->signal,
> > 					     status->chain_signal[1]);
> > 			break;
> > 		default:
> > 			break;
> > 		}
> >
> >
> > I could send a v2 or you can take care of that.
> >
> > Ryder
> >
> >