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. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
