Messages in this thread | | | Date | Mon, 18 Jan 2021 19:30:02 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default |
| |
On 2021-01-18 19:16, Geert Uytterhoeven wrote: > Hi Marc, > > On Mon, Jan 18, 2021 at 6:59 PM Marc Zyngier <maz@kernel.org> wrote: >> On 2021-01-18 17:39, Geert Uytterhoeven wrote: >> > On Fri, Dec 18, 2020 at 4:34 AM Saravana Kannan <saravanak@google.com> >> > wrote: >> >> Cyclic dependencies in some firmware was one of the last remaining >> >> reasons fw_devlink=on couldn't be set by default. Now that cyclic >> >> dependencies don't block probing, set fw_devlink=on by default. >> >> >> >> Setting fw_devlink=on by default brings a bunch of benefits >> >> (currently, >> >> only for systems with device tree firmware): >> >> * Significantly cuts down deferred probes. >> >> * Device probe is effectively attempted in graph order. >> >> * Makes it much easier to load drivers as modules without having to >> >> worry about functional dependencies between modules (depmod is still >> >> needed for symbol dependencies). >> >> >> >> If this patch prevents some devices from probing, it's very likely due >> >> to the system having one or more device drivers that "probe"/set up a >> >> device (DT node with compatible property) without creating a struct >> >> device for it. If we hit such cases, the device drivers need to be >> >> fixed so that they populate struct devices and probe them like normal >> >> device drivers so that the driver core is aware of the devices and >> >> their >> >> status. See [1] for an example of such a case. >> >> >> >> [1] - >> >> https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/ >> >> Signed-off-by: Saravana Kannan <saravanak@google.com> >> > >> > Shimoda-san reported that next-20210111 and later fail to boot >> > on Renesas R-Car Gen3 platforms. No output is seen, unless earlycon >> > is enabled. >> > >> > I have bisected this to commit e590474768f1cc04 ("driver core: Set >> > fw_devlink=on by default"). >> >> There is a tentative patch from Saravana here[1], which works around >> some issues on my RK3399 platform, and it'd be interesting to find >> out whether that helps on your system. >> >> Thanks, >> >> M. >> >> [1] >> https://lore.kernel.org/r/20210116011412.3211292-1-saravanak@google.com > > Thanks for the suggestion, but given no devices probe (incl. GPIO > providers), I'm afraid it won't help. [testing] Indeed. > > With the debug prints in device_links_check_suppliers enabled, and > some postprocessing, I get: > > 255 supplier e6180000.system-controller not ready > 9 supplier fe990000.iommu not ready > 9 supplier fe980000.iommu not ready > 6 supplier febd0000.iommu not ready > 6 supplier ec670000.iommu not ready > 3 supplier febe0000.iommu not ready > 3 supplier e7740000.iommu not ready > 3 supplier e6740000.iommu not ready > 3 supplier e65ee000.usb-phy not ready > 3 supplier e6570000.iommu not ready > 3 supplier e6054000.gpio not ready > 3 supplier e6053000.gpio not ready > > As everything is part of a PM Domain, the (lack of the) system > controller > must be the culprit. What's wrong with it? It is registered very early > in > the boot: > > [ 0.142096] rcar_sysc_pd_init:442: of_genpd_add_provider_onecell() > returned 0
Yeah, this looks like the exact same problem. The devlink stuff assumes that because there is a "compatible" property, there will be a driver directly associated with the node containing this property.
If any other node has a reference to that first node, the dependency will only get resolved if/when that first node is bound to a driver. Trouble is, there are *tons* of code in the tree that invalidate this heuristic, and for each occurrence of this we get another failure.
The patch I referred to papers over it by registering a dummy driver, but that doesn't scale easily...
M. -- Jazz is not dead. It just smells funny...
| |