On Mon, Jan 11, 2021 at 6:18 AM Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> wrote: > > On 11.01.2021 12:12, Marek Szyprowski wrote: > > On 18.12.2020 04:17, Saravana Kannan 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@xxxxxxxxxxxxxx/ > >> Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx> > > > > This patch landed recently in linux next-20210111 as commit > > e590474768f1 ("driver core: Set fw_devlink=on by default"). Sadly it > > breaks Exynos IOMMU operation, what causes lots of devices being > > deferred and not probed at all. I've briefly checked and noticed that > > exynos_sysmmu_probe() is never called after this patch. This is really > > strange for me, as the SYSMMU controllers on Exynos platform are > > regular platform devices registered by the OF code. The driver code is > > here: drivers/iommu/exynos-iommu.c, example dts: > > arch/arm/boot/dts/exynos3250.dtsi (compatible = "samsung,exynos-sysmmu"). > > Okay, I found the source of this problem. It is caused by Exynos power > domain driver, which is not platform driver yet. I will post a patch, > which converts it to the platform driver. Thanks Marek! Hopefully the debug logs I added were sufficient to figure out the reason. -Saravana
