Messages in this thread | | | From | Vladimir Oltean <> | Date | Sat, 4 May 2019 05:10:52 +0300 | Subject | Re: [PATCH net-next 5/9] net: dsa: Add support for deferred xmit |
| |
On Sat, 4 May 2019 at 05:07, Florian Fainelli <f.fainelli@gmail.com> wrote: > > > > On 5/3/2019 6:18 PM, Vladimir Oltean wrote: > > Some hardware needs to take some convincing work in order to receive > > frames on the CPU port (such as the sja1105 which takes temporary L2 > > forwarding rules over SPI that last for a single frame). Such work needs > > a sleepable context, and because the regular .ndo_start_xmit is atomic, > > this cannot be done in the tagger. So introduce a generic DSA mechanism > > that sets up a transmit skb queue and a workqueue for deferred > > transmission. > > > > The new driver callback (.port_deferred_xmit) is in dsa_switch and not > > in the tagger because the operations that require sleeping typically > > also involve interacting with the hardware, and not simply skb > > manipulations. Therefore having it there simplifies the structure a bit > > and makes it unnecessary to export functions from the driver to the > > tagger. > > > > The driver is responsible of calling dsa_enqueue_skb which transfers it > > to the master netdevice. This is so that it has a chance of performing > > some more work afterwards, such as cleanup or TX timestamping. > > > > To tell DSA that skb xmit deferral is required, I have thought about > > changing the return type of the tagger .xmit from struct sk_buff * into > > a enum dsa_tx_t that could potentially encode a DSA_XMIT_DEFER value. > > > > But the trailer tagger is reallocating every skb on xmit and therefore > > making a valid use of the pointer return value. So instead of reworking > > the API in complicated ways, right now a boolean property in the newly > > introduced DSA_SKB_CB is set. > > > > Signed-off-by: Vladimir Oltean <olteanv@gmail.com> > > --- > > [snip] > > > static inline struct dsa_port *dsa_slave_to_port(const struct net_device *dev) > > { > > struct dsa_slave_priv *p = netdev_priv(dev); > > diff --git a/net/dsa/slave.c b/net/dsa/slave.c > > index 8ad9bf957da1..cfb8cba6458c 100644 > > --- a/net/dsa/slave.c > > +++ b/net/dsa/slave.c > > @@ -120,6 +120,9 @@ static int dsa_slave_close(struct net_device *dev) > > struct net_device *master = dsa_slave_to_master(dev); > > struct dsa_port *dp = dsa_slave_to_port(dev); > > > > + cancel_work_sync(&dp->xmit_work); > > + skb_queue_purge(&dp->xmit_queue); > > + > > phylink_stop(dp->pl); > > Don't you also need to do that for dsa_slave_suspend() in case the > xmit() raced with netif_device_detach() somehow? > > > -- > Florian
Hi Florian, Thanks for pointing that out. Not having power management ops I didn't even think about that. -Vladimir
| |