Messages in this thread | | | From | Saravana Kannan <> | Date | Tue, 27 Apr 2021 14:05:20 -0700 | Subject | Re: [PATCH v1 3/3] Revert "Revert "driver core: Set fw_devlink=on by default"" |
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On Tue, Apr 27, 2021 at 9:47 AM Florian Fainelli <f.fainelli@gmail.com> wrote: > > > > On 4/27/2021 9:24 AM, Saravana Kannan wrote: > > On Tue, Apr 27, 2021 at 8:10 AM Sudeep Holla <sudeep.holla@arm.com> wrote: > >> > >> On Tue, Apr 27, 2021 at 03:11:16PM +0100, Cristian Marussi wrote: > >>> On Tue, Apr 27, 2021 at 09:33:31AM -0400, Jim Quinlan wrote: > >> [...] > >>>>> > >>>> I believe that the brcmstb-mbox node is in our DT for backwards > >>>> compatibility with our older Linux only. Note that we use the compatible > >>>> string '"arm,scmi-smc", "arm,scmi"'; the former chooses SMC transport and > >>>> ignores custom mailboxes such as brcmstb-mbox. > >>>> > >>> > >>> Right..so it is even more wrong that it is waiting for the mailboxes...but > >>> looking at the DT: > >>> > >>> brcm_scmi_mailbox@0 { > >>> #mbox-cells = <0x01>; > >>> compatible = "brcm,brcmstb-mbox"; > >>> status = "disabled"; > >>> linux,phandle = <0x04>; > >>> phandle = <0x04>; > >>> }; > >>> > >>> brcm_scmi@0 { > >>> compatible = "arm,scmi-smc\0arm,scmi"; > >>> mboxes = <0x04 0x00 0x04 0x01>; > >>> mbox-names = "tx\0rx"; > >>> shmem = <0x05>; > >>> status = "disabled"; > >>> arm,smc-id = <0x83000400>; > >>> interrupt-names = "a2p"; > >>> #address-cells = <0x01>; > >>> #size-cells = <0x00>; > >>> > >>> it seems to me that even though you declare an SMC based transport (and in fact > >>> you define the smc-id too) you also still define mboxes (as a fallback I suppose) > >>> referring to the brcm_scmi_mailbox phandle, and while this is ignored by the SCMI > >>> driver (because you have selected a compatible SMC transport) I imagine this dep > >>> is picked up by fw_devlink which in fact says: > >>> > >>>> [ 0.300086] platform brcm_scmi@0: Linked as a consumer to brcm_scmi_mailbox@0 > >>> > >>> and stalls waiting for it. (but I'm not really familiar on how fw_devlink > >>> internals works really...so I maybe off in these regards) > > > > Cristian, > > > > Great debugging work for not having worked on this before! Your > > comments about the dependencies are right. If you grep the logs for > > "probe deferral", you'll see these lines and more: > > > > [ 0.942998] platform brcm_scmi@0: probe deferral - supplier > > brcm_scmi_mailbox@0 not ready > > [ 3.622741] platform 8b20000.pcie: probe deferral - supplier > > brcm_scmi@0 not ready > > [ 5.695929] platform 840c000.serial: probe deferral - supplier > > brcm_scmi@0 not ready > > > > Florian, > > > > Sorry I wasn't clear in my earlier email. I was asking for the path to > > the board file DT in upstream so I could look at it and the files it > > references. I didn't mean to ask for an "decompiled" DTS attachment. > > The decompiled ones make it a pain to track the phandles. > > Our Device Tree sources are not in the kernel since the bootloader > provides a FDT to the kernel which is massaged in different ways to > support a single binary for a multitude of reference boards and chip > variants. That FDT is 90% auto-generated offline from scripts and about > 10% runtime patched based on our whim. We should probably still aim for > some visibility into these Device Tree files by the kernel community. > > > > > The part that's confusing to me is that the mbox node is disabled in > > the DT you attached. fw_devlink is smart enough to ignore disabled > > nodes. Is it getting enabled by the bootloader? Can you please try > > deleting the reference to the brcm_scmi_mailbox from the scmi node and > > see if it helps? Or leave it really disabled? > > Removing the 'mboxes' phandle works, see my other reply to Sudeep and I > should have captured the DT from the Linux prompt after it has been > finalized and where the mbox node is marked as enabled unfortunately. > > > > > Also, as a separate test of workarounds, can you please add > > deferred_probe_timeout=1 to your commandline and see if it helps? I'm > > assuming you have modules enabled? Otherwise, the existing smarts in > > fw_devlink to ignore devices with no drivers would have kicked in too. > > deferred_probe_timeout=1 does help however all of these drivers are > built into the kernel at the moment and so ultimately we reach > user-space with no console driver registered.
Whether all the required drivers are built in already or not doesn't matter for this workaround. fw_devlink can't tell if you are just about to load a module that'll probe the mailbox. If CONFIG_MODULES is disabled, then it can tell no more drivers are getting loaded by the time you hit late_initcall_sync() and it would have automatically applied this workaround without deferred_probe_timeout=1.
> > > > >> I was about to mention/ask the same when I saw Jim's reply. I see you have > >> already asked that. Couple of my opinions based on my very limited knowledge > >> on fw_devlink and how it works. > >> > >> 1. Since we have different compatible for SMC and mailbox, I am not sure > >> if it correct to leave mailbox information in scmi node. Once we have > >> proper yaml scheme, we must flag that error IMO. > >> > >> 2. IIUC, the fw_devlink might use information from DT to establish the > >> dependency and having mailbox information in this context may be > >> considered wrong as there is no dependency if it is using SMC. > > > > If this mbox reference from scmi is wrong for the current kernel and > > never used, then I'd recommend deleting that. > > Yes that seems to be the way forward unless we want to set > fw_devlink=permissive on the command line, either should hopefully be an > option.
I read all the other emails from Sudeep, Geert and you. I'll just respond to all of them here.
My preferred order of the workarouds: 1. Fix the DT sent to the kernel. 2. If deferred_probe_timeout=1 doesn't break anything else, use that. This is better than (4). 3. Geert's early boot quirk suggestion. 4. fw_devlink=permissive (least preferred because this might mask issues with fw_devlink=on in your future changes).
Changing the SCMI driver itself won't help fw_devlink.
Thanks, Saravana
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