On Wed, 26 Jun 2019 at 01:58, Russell King - ARM Linux admin <li...@armlinux.org.uk> wrote: > > On Wed, Jun 26, 2019 at 01:14:59AM +0300, Vladimir Oltean wrote: > > On Wed, 26 Jun 2019 at 00:53, Russell King - ARM Linux admin > > <li...@armlinux.org.uk> wrote: > > > > > > On Tue, Jun 25, 2019 at 11:24:01PM +0300, Vladimir Oltean wrote: > > > > Hi Russell, > > > > > > > > On 6/24/19 6:39 PM, Russell King - ARM Linux admin wrote: > > > > > This should be removed - state->link is not for use in mac_config. > > > > > Even in fixed mode, the link can be brought up/down by means of a > > > > > gpio, and this should be dealt with via the mac_link_* functions. > > > > > > > > > > > > > What do you mean exactly that state->link is not for use, is that true > > > > in > > > > general? > > > > > > Yes. mac_config() should not touch it; it is not always in a defined > > > state. For example, if you set modes via ethtool (the > > > ethtool_ksettings_set API) then state->link will probably contain > > > zero irrespective of the true link state. > > > > > > > Experimentally, state->link is zero at the same time as state->speed > > is -1, so just ignoring !state->link made sense. This is not in-band > > AN. What is your suggestion? Should I proceed to try and configure the > > MAC for SPEED_UNKNOWN? > > What would you have done with a PHY when the link is down, what speed > would you have configured in the phylib adjust_link callback? phylib > also sets SPEED_UNKNOWN/DUPLEX_UNKNOWN when the link is down. >
With phylib, I'd make the driver ignore the speed and do nothing. With phylink, I'd make the core not call mac_config. But what happened is I saw phylink call mac_config anyway, said 'weird' and proceeded to ignore it as I would have for phylib. I'm just not understanding your position - it seems like you're implying there's a bug in phylink and the function call with MLO_AN_FIXED, state->link=0 and state->speed=-1 should not have taken place, which is what I wanted to confirm. > What we do in Marvell drivers is set to the lowest speed (10M) in such > cases, which is fine as the MAC supports 10M. > > It wouldn't be appropriate for phylink to force something on MAC > drivers, it's easier if the MAC just defaults SPEED_UNKNOWN to something > itself. > > > > > > It exists in this structure because it was convenient to just use one > > > structure to store all the link information in various parts of the > > > code, and when requesting the negotiated in-band MAC configuration. > > > > > > I've come to the conclusion that that decision was a mistake, based > > > on patches such as the above mistakenly thinking that everything in > > > the state structure is fair game. I've since updated the docs to > > > explicitly spell it out, but I'm also looking at the feasibility of > > > changing the mac_config() interface entirely - splitting it into two > > > (mac_config_fixed() and mac_config_inband()) and passing only the > > > appropriate parameters to each. > > > > > > However, having looked at that, I think such a change will make some > > > MAC drivers quite a bit more complicated - having all the config > > > steps in one method appears to make the configuration of MAC drivers > > > easier (eg, mvneta, mvpp2.) > > > > > > > In drivers/net/dsa/sja1105/sja1105_main.c, if I remove the "if > > > > (!state->link)" guard, I see PHYLINK calls with a SPEED_UNKNOWN > > > > argument for > > > > ports that are BR_STATE_DISABLED. Is that normal? > > > > > > This looks like another driver which has been converted to phylink > > > without my review; I certainly wasn't aware of it. It gets a few > > > things wrong, such as: > > > > > > 1) not checking state->interface in the validate callback - so it > > > is basically saying that it can support any PHY interface mode > > > that the kernel happens to support. > > > > > > > Partially true. It does check the DT bindings for supported MII modes > > in sja1105_init_mii_settings (for fundamental reasons... the switch > > expects an 'all-in-one' configuration buffer with the operating modes > > of all MACs - don't ask me to delay the uploading of this static > > config until all ports collected their interface_mode from phylink via > > the mac_config callback - it's a deadlock). > > Ok, so you need to reject interface modes that are not compatible > with the currently configured mode in the validate() callback, but > please keep PHY_INTERFACE_MODE_NA reporting back the capabilities. > (this is now documented.) > Ok. > > It is a gigabit switch with MII/RMII/RGMII MACs - I have never seen > > any PHY wired for these modes that can change system interface type. > > It is unlikely that MII/RMII/RGMII will switch modes, but in terms of > correct implementation, sticking to the way the function is expected > to behave means that I don't get surprises when changing phylink layer > in the future. > > > > > > 2) if phylink is configured to use in-band, then state->speed is > > > undefined; this driver will fail. (If folk don't want to support > > > that, we ought to have a way to tell phylink to reject anything > > > that attempts to set it to in-band mode!) > > > > > > > Ok. > > > > > 3) it doesn't implement phylink_mac_link_state DSA ops, so it doesn't > > > support SGMII or 802.3z phy interface modes (see 1). > > > > > > > No, it doesn't. > > Some odd switch in this device family supports SGMII on 1 of its > > ports, however I haven't put my hands on it. > > When I do I'll add checks for strange scenarios, like connecting it to > > an Aquantia PHY that can switch between SGMII and USXGMII (although > > why would anyone pair a 10G capable PHY to a 1G capable MAC...) > > It's unlikely that it would switch between SGMII and USXGMII > dynamically, as USXGMII supports speeds from 10G down to 10M. > > Where interface mode switching tends to be used is with modes such > as 10GBASE-R, which doesn't support anything except 10G. In order > for the PHY to operate at slower speeds, it has a few options: > > 1) perform rate adaption. > 2) dynamically switch interface type to an interface type that > supports the desired speed. > 3) just not support slower speeds. > So am I reading this correctly - it kind of makes sense for gigabit MAC drivers to not check for the MII interface changing protocol? > -- > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ > FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up > According to speedtest.net: 11.9Mbps down 500kbps up Thanks, -Vladimir
