From mboxrd@z Thu Jan 1 00:00:00 1970 From: Florian Fainelli Subject: Re: [PATCH 1/3] fixed_phy: handle link-down case Date: Fri, 17 Jul 2015 16:35:20 -0700 Message-ID: <55A99138.2030905@gmail.com> References: <55A7C45F.1070501@list.ru> <55A7C49E.2020803@list.ru> <55A83D86.2030505@gmail.com> <55A8E64A.3040009@list.ru> <55A94E5A.9010104@gmail.com> <55A95F83.8010900@list.ru> <55A97B51.3030508@gmail.com> <55A98EC5.4040805@list.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Linux kernel , Sebastien Rannou , Arnaud Ebalard , Stas Sergeev To: Stas Sergeev , netdev Return-path: In-Reply-To: <55A98EC5.4040805@list.ru> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 17/07/15 16:24, Stas Sergeev wrote: > 18.07.2015 01:01, Florian Fainelli =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 17/07/15 13:03, Stas Sergeev wrote: >>> 17.07.2015 21:50, Florian Fainelli =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> On 17/07/15 04:26, Stas Sergeev wrote: >>>>> 17.07.2015 02:25, Florian Fainelli =D0=BF=D0=B8=D1=88=D0=B5=D1=82= : >>>>>> On 16/07/15 07:50, Stas Sergeev wrote: >>>>>>> Currently fixed_phy driver recognizes only the link-up state. >>>>>>> This simple patch adds an implementation of link-down state. >>>>>>> It fixes the status registers when link is down, and also allow= s >>>>>>> to register the fixed-phy with link down without specifying the >>>>>>> speed. >>>>>> This patch still breaks my setups here, e.g: >>>>>> drivers/net/dsa/bcm_sf2.c, >>>>>> but I will look into it. >>>>>> >>>>>> Do we really need this for now for your two other patches to wor= k >>>>>> properly, or is it just nicer to have? >>>>> Yes, absolutely. >>>>> Otherwise registering fixed phy will return -EINVAL >>>>> because of the missing link speed (even though the link >>>>> is down). >>>> Ok, I see the problem that you have now. Arguably you could say th= at >>>> according to the fixed-link binding, speed needs to be specified a= nd >>>> the >>>> code correctly errors out with such an error if you do not specify >>>> it. I >>> Aren't you missing the fact that .link=3D0? >>> I think what you say is true only for the link-up case, no? >>> .speed=3D=3D0 is valid for link-down IMHO: no link - zero speed. >> Pardon me being very dense and stupid here, but your problem is that= the >> "speed" parameter is not specified in your DT, > Not even a fixed-link at all, since the latest patches. > I removed fixed-link defs from my DT. Hummm, okay, so you just have the inband-status property and that's it, not even a fixed-link node anymore, right? How does mvneta_fixed_link_update() work then since it needs a fixed PHY to be registered? >=20 >> and we end-up returning >> -EINVAL from of_phy_register_fixed_link(), is that what is happening= ? > Yes. >=20 >> And even if we silenced that error, > I don't agree with calling it an error silencing. > To me it is a fix. It will also return a more correct status when > link is down. >=20 >> we would end-up calling >> fixed_phy_add() which would also return -EINVAL because then, we wou= ld >> have status.link =3D 1, but no speed. > Why link=3D1 and no speed? This is not valid, should never > be used. The error checking is still there to prevent it. >=20 >> So I better understand what is it >> that you are after here, and that is also a broken Device Tree, is n= ot >> it? > I don't understand. If you didn't specify the in-band status, you > _must_ set the speed. There is no broken DT in either case. >=20 >> So this was the reason why in earlier versions of the patchset you >> ended-up with a given speed which would make us pass this condition, >> right? > As explained earlier, yes. >=20 >=20 >>>> So is different is that I use a link_update callback, and so we re= ly on >>>> at least one call of this function to initialize the hardware in >>>> drivers/net/dsa/bcm_sf2.c >>> Do you mean this?: >>> core_writel(priv, reg, CORE_STS_OVERRIDE_GMIIP_PORT(port)); >>> Maybe just moving the HW initialization bits to some init func >>> will be a quick fix? >> Well, the problem with that is that to know how we should be configu= ring >> the hardware in the adjust_link function, we need to run the link_up= date >> function first. By default, there is no auto-negotiation on these fi= xed >> links at all, so we cannot rely on any value being programmed other = than >> those specified in DT. > Ah, so is my understanding correct that in fixed_link_update() > you set .link=3D0 and as a result get wrong speed in adjust_link(), > which gets then written to init HW? Yes, that's what happens. > AFAIK when link is down, you are not allowed to rely on the PHY > status registers to read speed from, or am I wrong? So if my > understanding is correct, this was working by a pure luck. Well, it's more like it is undefined, and before this patch, the fixed PHY would update everything except the link status indication. > As for the quick fix - why not to do this pre-init in fixed_link_upda= te() > instead of adjust_link()? In fixed_link_update() you'll get the speed > right from DT, so it will be correct. fixed_link_update() only gets called once you start your PHY state machine, unfortunately, not upon fixed PHY device registration, and it runs before your adjust_link callback does, that's why starting with correct parameters is kind of important here. Of course, this could be fixed. >=20 >> The changes are not trivial, it took a while to get that logic done > For a longer term fix, > how about adding a *status arg to of_phy_register_fixed_link() to > always get the status back to the driver, unless NULL is provided? > Using an update callback for that doesn't look like the best thing > to do. And besides, if we move to my fixed_phy_update_state(), > this will be needed anyway. I agree that the link_update callback is not the best thing, it polls the hardware and comes with that problem that it may or may not have ye= t run to configure your fixed_phy_status appropriately. --=20 =46lorian