Hi Russell, On Tue, Oct 03, 2023 at 02:14:41PM +0100, Russell King (Oracle) wrote: > On Sat, Sep 23, 2023 at 04:49:04PM +0300, Vladimir Oltean wrote: > > +static int lynx_pcs_parse_fwnode(struct lynx_pcs *lynx) > > +{ > > + struct fwnode_handle *node = lynx->mdio->dev.fwnode; > > + enum mtip_model model = MTIP_MODEL_AUTODETECT; > > + struct device_node *np = to_of_node(node); > > + struct mdio_device *mdio = lynx->mdio; > > + struct device *dev = &mdio->dev; > > + struct phy *phy; > > + int i, err; > > + > > + if (!node) > > + return 0; > > + > > + lynx->backplane_mode = fwnode_property_present(node, "fsl,backplane-mode"); > > + if (!lynx->backplane_mode) > > + return 0; > > + > > + if (fwnode_device_is_compatible(node, "fsl,lx2160a-lynx-pcs")) > > + model = MTIP_MODEL_LX2160A; > > + > > + lynx->num_lanes = of_count_phandle_with_args(np, "phys", "#phy-cells"); > > + if (lynx->num_lanes < 0) > > + return lynx->num_lanes; > > Is it possible for ->num_lanes to be zero at this point? If that is > possible, then ->anlt[PRIMARY_LANE] will be NULL but ->backplane_mode > will be set, so won't that cause the mtip_* calls above to pass a > NULL pointer into those functions? Is that safe? Should we trap that > case here? Assuming the dt-bindings as proposed here, that case would be an invalid device tree ("fsl,backplane-mode" present but "phys" isn't present), which I indeed failed to catch. But in my reply to Krzysztof here: https://lore.kernel.org/netdev/20231002121958.xybzovgjzldfiae2@skbuf/ I said that for v3, I'm looking to move the "phys" property from the PCS to the MAC (it's already in the MAC for the non-backplane use cases). On LS1028A (ENETC, Felix), the lynx-pcs is not OF-based (we use lynx_pcs_create_mdiodev()), but it would be good to support the 1000Base-KX link mode there also. As I'm starting to look beyond LX2160A, I'm starting to see why adding extra dt-bindings to the lynx-pcs (both "phys" and "fsl,backplane-mode") will be problematic if there is no OF node to speak of. I will leave a separate comment with some new ideas. > If that's correct, then I don't see any point in storing > ->backplane_mode, since we can then use ->num_lanes > PRIMARY_LANE > or similar instead. Well, in v3, my plan is for the caller of lynx_pcs_create() (aka the MAC) to always pass an array of phys (the ones from its own OF node). In that case, we would indeed need the "fsl,backplane-mode" property in the PCS, because otherwise, with your proposal, the PCS would instantiate the AN/LT block even when it's not expected. > > + > > + if (WARN_ON(lynx->num_lanes > MAX_NUM_LANES)) > > + return -EINVAL; > > Do we need to use WARN_ON() here, or would it be better to print a short > error-level message? Admittedly I may not have the best intuition here, but I didn't want to over-complicate the code with error messages that can only be triggered with invalid device trees. > > + > > + for (i = 0; i < lynx->num_lanes; i++) { > > + phy = devm_of_phy_get_by_index(dev, np, i); > > + if (IS_ERR(phy)) > > + return dev_err_probe(dev, PTR_ERR(phy), > > + "Failed to get SerDes PHY %d\n", i); > > + > > + lynx->anlt[i] = mtip_backplane_create(mdio, phy, model); > > + if (IS_ERR(lynx->anlt[i])) { > > + err = PTR_ERR(lynx->anlt[i]); > > + > > + while (i-- > 0) > > + mtip_backplane_destroy(lynx->anlt[i]); > > + > > + return err; > > + } > > + } > > + > > + for (i = 1; i < lynx->num_lanes; i++) { > > + err = mtip_backplane_add_subordinate(lynx->anlt[PRIMARY_LANE], > > + lynx->anlt[i]); > > + if (WARN_ON(err)) { > > Again, does this need to be a backtrace-producing WARN_ON()? mtip_backplane_add_subordinate() will only return -ERANGE if called too many times (more than MTIP_MAX_NUM_SUBORDINATES times, aka more than "MAX_NUM_LANES - 1" times). Given the way that the code is constructed, it is technically impossible for that to happen, but only because MTIP_MAX_NUM_SUBORDINATES is hand-crafted to be 3 and MAX_NUM_LANES to be 4. I think that if I define MTIP_MAX_NUM_SUBORDINATES in terms of MAX_NUM_LANES - 1, I can simply make mtip_backplane_add_subordinate() return void. What I want to avoid is to add error handling for errors which cannot take place. Which is where the WARN_ON() came from. > > + /* Too many SerDes lanes in the device tree? */ > > + for (i = 0; i < lynx->num_lanes; i++) > > + mtip_backplane_destroy(lynx->anlt[i]); > > + return err; > > + } > > + } > > + > > + return 0; > > +} > > + > > static struct phylink_pcs *lynx_pcs_create(struct mdio_device *mdio) > > { > > struct lynx_pcs *lynx; > > + int err; > > > > lynx = kzalloc(sizeof(*lynx), GFP_KERNEL); > > if (!lynx) > > @@ -327,6 +451,12 @@ static struct phylink_pcs *lynx_pcs_create(struct mdio_device *mdio) > > lynx->pcs.neg_mode = true; > > lynx->pcs.poll = true; > > > > + err = lynx_pcs_parse_fwnode(lynx); > > + if (err) { > > + kfree(lynx); > > + return ERR_PTR(err); > > + } > > + > > return lynx_to_phylink_pcs(lynx); > > } > > > > @@ -392,6 +522,11 @@ EXPORT_SYMBOL_GPL(lynx_pcs_create_fwnode); > > void lynx_pcs_destroy(struct phylink_pcs *pcs) > > { > > struct lynx_pcs *lynx = phylink_pcs_to_lynx(pcs); > > + int i; > > + > > + if (lynx->backplane_mode) > > + for (i = 0; i < lynx->num_lanes; i++) > > + mtip_backplane_destroy(lynx->anlt[i]); > > Won't ->num_lanes only be non-zero when ->backplane_mode is set, so > isn't the test for ->backplane_mode redundant here? I think it won't be redundant anymore once the series reaches a less "WIP" state. > > > > mdio_device_put(lynx->mdio); > > kfree(lynx); > > -- > > 2.34.1 > > > > > > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!