netdev - Re: [PATCH net-next 3/5] net: bcmasp: Add support for ASP2.0 Ethernet controller

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Message-ID: <CAJx26kVw8iJD_wJXypF4gjx697z_ErOdogWNNQffis19pt6y_w@mail.gmail.com>
Date:   Wed, 29 Sep 2021 16:04:53 -0700
From:   Justin Chen <justinpopo6@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Doug Berger <opendmb@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Rafał Miłecki <rafal@...ecki.pl>,
        Randy Dunlap <rdunlap@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Michael Chan <michael.chan@...adcom.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <dri-devel@...ts.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH net-next 3/5] net: bcmasp: Add support for ASP2.0 Ethernet controller

On Sun, Sep 26, 2021 at 6:58 AM Andrew Lunn <andrew@...n.ch> wrote:
>
> > > > +static int bcmasp_set_priv_flags(struct net_device *dev, u32 flags)
> > > > +{
> > > > + struct bcmasp_intf *intf = netdev_priv(dev);
> > > > +
> > > > + intf->wol_keep_rx_en = flags & BCMASP_WOL_KEEP_RX_EN ? 1 : 0;
> > > > +
> > > > + return 0;
> > >
> > > Please could you explain this some more. How can you disable RX and
> > > still have WoL working?
> >
> > Wake-on-LAN using Magic Packets and network filters requires keeping the
> > UniMAC's receiver turned on, and then the packets feed into the Magic Packet
> > Detector (MPD) block or the network filter block. In that mode DRAM is in
> > self refresh and there is local matching of frames into a tiny FIFO however
> > in the case of magic packets the packets leading to a wake-up are dropped as
> > there is nowhere to store them. In the case of a network filter match (e.g.:
> > matching a multicast IP address plus protocol, plus source/destination
> > ports) the packets are also discarded because the receive DMA was shut down.
> >
> > When the wol_keep_rx_en flag is set, the above happens but we also allow the
> > packets that did match a network filter to reach the small FIFO (Justin
> > would know how many entries are there) that is used to push the packets to
> > DRAM. The packet contents are held in there until the system wakes up which
> > is usually just a few hundreds of micro seconds after we received a packet
> > that triggered a wake-up. Once we overflow the receive DMA FIFO capacity
> > subsequent packets get dropped which is fine since we are usually talking
> > about very low bit rates, and we only try to push to DRAM the packets of
> > interest, that is those for which we have a network filter.
> >
> > This is convenient in scenarios where you want to wake-up from multicast DNS
> > (e.g.: wake on Googlecast, Bonjour etc.) because then the packet that
> > resulted in the system wake-up is not discarded but is then delivered to the
> > network stack.
>
> Thanks for the explanation. It would be easier for the user if you
> automate this. Enable is by default for WoL types which have user
> content?
>
Yup that can work. We can enable it for WAKE_FILTER type wol and leave
it disabled otherwise.

> > > > + /* Per ch */
> > > > + intf->tx_spb_dma = priv->base + TX_SPB_DMA_OFFSET(intf);
> > > > + intf->res.tx_spb_ctrl = priv->base + TX_SPB_CTRL_OFFSET(intf);
> > > > + /*
> > > > +  * Stop gap solution. This should be removed when 72165a0 is
> > > > +  * deprecated
> > > > +  */
> > >
> > > Is that an internal commit?
> >
> > Yes this is a revision of the silicon that is not meant to see the light of
> > day.
>
> So this can all be removed?
>
Yup. That can be removed

>    Andrew

Thanks for the review.

Justin