Date:   Mon, 17 Jan 2022 18:38:25 -0500
From:   Alexander Aring <alex.aring@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan - ML <linux-wpan@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        Michael Hennerich <michael.hennerich@...log.com>,
        Harry Morris <h.morris@...coda.com>,
        Varka Bhadram <varkabhadram@...il.com>,
        Xue Liu <liuxuenetmail@...il.com>, Alan Ott <alan@...nal11.us>,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        "linux-wireless@...r.kernel.org Wireless" 
        <linux-wireless@...r.kernel.org>
Subject: Re: [wpan-next v2 08/27] net: ieee802154: Drop symbol duration
 settings when the core does it already

Hi,

On Mon, 17 Jan 2022 at 04:12, Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>
> Hi Alexander,
>
> alex.aring@...il.com wrote on Sun, 16 Jan 2022 18:21:16 -0500:
>
> > Hi,
> >
> > On Fri, 14 Jan 2022 at 05:21, Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > >
> > > Hi Alexander,
> > >
> > > alex.aring@...il.com wrote on Thu, 13 Jan 2022 18:34:00 -0500:
> > >
> > > > Hi,
> > > >
> > > > On Thu, 13 Jan 2022 at 06:16, Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > > > >
> > > > > Hi Alexander,
> > > > >
> > > > > alex.aring@...il.com wrote on Wed, 12 Jan 2022 17:26:14 -0500:
> > > > >
> > > > > > Hi,
> > > > > >
> > > > > > On Wed, 12 Jan 2022 at 12:33, Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > > > > > >
> > > > > > > The core now knows how to set the symbol duration in a few cases, when
> > > > > > > drivers correctly advertise the protocols used on each channel. For
> > > > > > > these drivers, there is no more need to bother with symbol duration, so
> > > > > > > just drop the duplicated code.
> > > > > > >
> > > > > > > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> > > > > > > ---
> > > > > > >  drivers/net/ieee802154/ca8210.c | 1 -
> > > > > > >  drivers/net/ieee802154/mcr20a.c | 2 --
> > > > > > >  2 files changed, 3 deletions(-)
> > > > > > >
> > > > > > > diff --git a/drivers/net/ieee802154/ca8210.c b/drivers/net/ieee802154/ca8210.c
> > > > > > > index 82b2a173bdbd..d3a9e4fe05f4 100644
> > > > > > > --- a/drivers/net/ieee802154/ca8210.c
> > > > > > > +++ b/drivers/net/ieee802154/ca8210.c
> > > > > > > @@ -2977,7 +2977,6 @@ static void ca8210_hw_setup(struct ieee802154_hw *ca8210_hw)
> > > > > > >         ca8210_hw->phy->cca.mode = NL802154_CCA_ENERGY_CARRIER;
> > > > > > >         ca8210_hw->phy->cca.opt = NL802154_CCA_OPT_ENERGY_CARRIER_AND;
> > > > > > >         ca8210_hw->phy->cca_ed_level = -9800;
> > > > > > > -       ca8210_hw->phy->symbol_duration = 16 * 1000;
> > > > > > >         ca8210_hw->phy->lifs_period = 40;
> > > > > > >         ca8210_hw->phy->sifs_period = 12;
> > > > > > >         ca8210_hw->flags =
> > > > > > > diff --git a/drivers/net/ieee802154/mcr20a.c b/drivers/net/ieee802154/mcr20a.c
> > > > > > > index 8aa87e9bf92e..da2ab19cb5ee 100644
> > > > > > > --- a/drivers/net/ieee802154/mcr20a.c
> > > > > > > +++ b/drivers/net/ieee802154/mcr20a.c
> > > > > > > @@ -975,7 +975,6 @@ static void mcr20a_hw_setup(struct mcr20a_local *lp)
> > > > > > >
> > > > > > >         dev_dbg(printdev(lp), "%s\n", __func__);
> > > > > > >
> > > > > > > -       phy->symbol_duration = 16 * 1000;
> > > > > > >         phy->lifs_period = 40;
> > > > > > >         phy->sifs_period = 12;
> > > > > > >
> > > > > > > @@ -1010,7 +1009,6 @@ static void mcr20a_hw_setup(struct mcr20a_local *lp)
> > > > > > >         phy->current_page = 0;
> > > > > > >         /* MCR20A default reset value */
> > > > > > >         phy->current_channel = 20;
> > > > > > > -       phy->symbol_duration = 16 * 1000;
> > > > > > >         phy->supported.tx_powers = mcr20a_powers;
> > > > > > >         phy->supported.tx_powers_size = ARRAY_SIZE(mcr20a_powers);
> > > > > > >         phy->cca_ed_level = phy->supported.cca_ed_levels[75];
> > > > > >
> > > > > > What's about the atrf86230 driver?
> > > > >
> > > > > I couldn't find reliable information about what this meant:
> > > > >
> > > > >         /* SUB:0 and BPSK:0 -> BPSK-20 */
> > > > >         /* SUB:1 and BPSK:0 -> BPSK-40 */
> > > > >         /* SUB:0 and BPSK:1 -> OQPSK-100/200/400 */
> > > > >         /* SUB:1 and BPSK:1 -> OQPSK-250/500/1000 */
> > > > >
> > > > > None of these comments match the spec so I don't know what to put
> > > > > there. If you know what these protocols are, I will immediately
> > > > > provide this information into the driver and ensure the core handles
> > > > > these durations properly before dropping the symbol_durations settings
> > > > > from the code.
> > > >
> > > > I think those are from the transceiver datasheets (which are free to
> > > > access). Can you not simply merge them or is there a conflict?
> > >
> > > Actually I misread the driver, it supports several kind of chips with
> > > different channel settings and this disturbed me. I downloaded the
> > > datasheet and figured that the number after the protocol is the bit
> > > rate. This helped me to make the connection with what I already know,
> > > so both atusb and atrf86230 drivers have been converted too.
> >
> > and what is about hwsim? I think the table gets too large then...
>
> I'm sorry but I don't follow you here, what do you mean by "the table
> gets too large"?
>

The switch/case statements getting large to support the channels which
hwsim supports.

> > that's why I was thinking of moving that somehow to the regdb, however
> > this is another project as I said and this way is fine. Maybe we use a
> > kind of fallback then? The hwsim phy isn't really any 802.15.4 PHY,
> > it's just memcpy() but it would be nice to be able to test scan with
> > it. So far I understand it is already possible to make something with
> > hwsim here but what about the zero symbol rate and the "waiting
> > period" is zero?
>
> Before this series: many drivers would not set the symbol duration
> properly. In this case the scan will likely not work because wait
> periods will be too short. But that's how it is, we miss some
> information.
>

This is the case because not every transceiver was using lifs/sifs handling.

> But for hwsim, I've handled a lot of situations so yes, there are
> still channels that won't have a proper symbol duration because I just
> don't know them, but for most of them (several pages) it will work like
> a charm.
>
> >
> > btw:
> > Also for testing with hwsim and the missing features which currently
> > exist. Can we implement some user space test program which replies
> > (active scan) or sends periodically something out via AF_PACKET raw
> > and a monitor interface that should work to test if it is working?
>
> We already have all this handled, no need for extra software. You can
> test active and passive scans between two hwsim devices already:
>
> # iwpan dev wpan0 beacons send interval 15
> # iwpan dev wpan1 scan type active duration 1
> # iwpan dev wpan0 beacons stop
>
> or
>
> # iwpan dev wpan0 beacons send interval 1
> # iwpan dev wpan1 scan type passive duration 2
> # iwpan dev wpan0 beacons stop
>
> > Ideally we could do that very easily with scapy (not sure about their
> > _upstream_ 802.15.4 support). I hope I got that right that there is
> > still something missing but we could fake it in such a way (just for
> > hwsim testing).
>
> I hope the above will match your expectations.
>

I need to think and read more about... in my mind is currently the
following question: are not coordinators broadcasting that information
only? Means, isn't that a job for a coordinator?

Thanks.

- Alex

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