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

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Date:   Mon, 10 Jun 2019 12:22:21 +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 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