On Fri, May 02, 2025 at 06:54:49PM +0100, Russell King (Oracle) wrote: > On Fri, May 02, 2025 at 05:29:21PM +0200, Andrew Lunn wrote: > > On Fri, May 02, 2025 at 02:35:36PM +0100, Russell King (Oracle) wrote: > > > Phylink does not permit drivers to mess with the netif carrier, as > > > this will de-synchronise phylink with the MAC driver. Moreover, > > > setting and clearing the TE and RE bits via stmmac_mac_set() in this > > > path is also wrong as the link may not be up. > > > > > > Replace the netif_carrier_on(), netif_carrier_off() and > > > stmmac_mac_set() calls with the appropriate phylink_carrier_block() and > > > phylink_carrier_unblock() calls, thereby allowing phylink to manage the > > > netif carrier and TE/RE bits through the .mac_link_up() and > > > .mac_link_down() methods. > > > > > > This change will have the side effect of printing link messages to > > > the kernel log, even though the physical link hasn't changed state. > > > This matches the carrier state that userspace sees, which has always > > > "bounced". > > > > > > Note that RE should only be set after the DMA is ready to avoid the > > > receive FIFO between the MAC and DMA blocks overflowing, so > > > phylink_start() needs to be placed after DMA has been started. > > > > > > Signed-off-by: Russell King (Oracle) <rmk+kernel@xxxxxxxxxxxxxxx> > > > --- > > > .../net/ethernet/stmicro/stmmac/stmmac_main.c | 20 +++++++++++-------- > > > 1 file changed, 12 insertions(+), 8 deletions(-) > > > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > index f59a2363f150..ac27ea679b23 100644 > > > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > @@ -6922,6 +6922,11 @@ void stmmac_xdp_release(struct net_device *dev) > > > /* Ensure tx function is not running */ > > > netif_tx_disable(dev); > > > > > > + /* Take down the software link. stmmac_xdp_open() must be called after > > > + * this function to release this block. > > > + */ > > > + phylink_carrier_block(priv->phylink); > > > + > > > /* Disable NAPI process */ > > > stmmac_disable_all_queues(priv); > > > > > > @@ -6937,14 +6942,10 @@ void stmmac_xdp_release(struct net_device *dev) > > > /* Release and free the Rx/Tx resources */ > > > free_dma_desc_resources(priv, &priv->dma_conf); > > > > > > - /* Disable the MAC Rx/Tx */ > > > - stmmac_mac_set(priv, priv->ioaddr, false); > > > - > > > /* set trans_start so we don't get spurious > > > * watchdogs during reset > > > */ > > > netif_trans_update(dev); > > > - netif_carrier_off(dev); > > > } > > > > > > > > int stmmac_xdp_open(struct net_device *dev) > > > @@ -7026,25 +7027,28 @@ int stmmac_xdp_open(struct net_device *dev) > > > hrtimer_setup(&tx_q->txtimer, stmmac_tx_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > > > } > > > > > > - /* Enable the MAC Rx/Tx */ > > > - stmmac_mac_set(priv, priv->ioaddr, true); > > > - > > > /* Start Rx & Tx DMA Channels */ > > > stmmac_start_all_dma(priv); > > > > > > + /* Allow phylink to bring the software link back up. > > > + * stmmac_xdp_release() must have been called prior to this. > > > + */ > > > > This is counter intuitive. Why is release called before open? > > Indeed - and that should've been caught in the review where XDP was > being added. > > > Looking into stmmac_xdp_set_prog() i think i get it. Even if there is > > not a running XDP prog, stmmac_xdp_release() is called, and then > > stmmac_xdp_open(). > > If there is a change of "do we have an XDP prog" state, then > stmmac_xdp_release() is called to free all the current contexts to > do with queue/descriptor management, and then stmmac_xdp_open() is > called thereafter. These are doing a subset of .ndo_open/.ndo_release > and I think that's where they're getting their naming from. > > The only possible sequence is: > > stmmac_open() > then, on each XDP prog addition or removal, but not replacement: > stmmac_xdp_release() > stmmac_xdp_open() > finally, > stmmac_release() > > > Maybe these two functions need better names? prepare and commit? > > Yes, it's all counter intuitive, and there are various things about the > XDP code that make it hard to follow. > > For example, stmmac_xdp_set_prog() leads you to think, because of the > way the need_update variable is set, that looking for references to > xdp_prog would show one where all the dependents are, but no, there's > stmmac_xdp_is_enabled(), which is nice and readable, but could've > been used in stmmac_xdp_set_prog() to make it more obvious what to > grep for. > > Incidentally, if stmmac_xdp_open() fails to re-grab the interrupts, > then it calls phylink_stop(), stmmac_hw_teardown(), and > free_dma_desc_resources(). > > If one then set the interface administratively down, stmmac_release() > gets called, which again calls phylink_stop(), free_dma_desc_resources() > and stmmac_release_ptp(). > > stmmac_release_ptp() disables/unprepares clk_ptp_ref, and unregisters > the PTP stuff. stmmac_hw_teardown() also disables/unprepares > clk_ptp_ref, so we probably unbalance the clk API in this case... > and probably much other stuff. > > Calling free_dma_desc_resources() twice calls functios such as > free_dma_tx_desc_resources() twice, and it looks like that's not going > to be healthy, calling dma_free_coherent() with the same arguments, > double-releasing memory. Same for kfree(). Probably same for the RX > stuff. > > Basically, if one messes with XDP in this driver, expect things to go > bang and kill the kernel if something goes wrong with the whole > xdp_release+xdp_open dance. > > Honestly, this needs a rewrite, but I currently know nowt about XDP. > > So, I'd suggest that the names of these functions is the least of the > problems here. Well, this series has been discarded from patchwork. Shrug. I won't be posting another version, stmmac can remain broken. I don't have a suggestion on better names for these functions. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
