01.10.2020 05:48, Nicolin Chen пишет: > On Thu, Oct 01, 2020 at 05:06:19AM +0300, Dmitry Osipenko wrote: >> 01.10.2020 04:26, Nicolin Chen пишет: >>> On Thu, Oct 01, 2020 at 12:56:46AM +0300, Dmitry Osipenko wrote: >>>> 01.10.2020 00:32, Nicolin Chen пишет: >>>>> On Thu, Oct 01, 2020 at 12:24:25AM +0300, Dmitry Osipenko wrote: >>>>>> ... >>>>>>>> It looks to me like the only reason why you need this new global API is >>>>>>>> because PCI devices may not have a device tree node with a phandle to >>>>>>>> the IOMMU. However, SMMU support for PCI will only be enabled if the >>>>>>>> root complex has an iommus property, right? In that case, can't we >>>>>>>> simply do something like this: >>>>>>>> >>>>>>>> if (dev_is_pci(dev)) >>>>>>>> np = find_host_bridge(dev)->of_node; >>>>>>>> else >>>>>>>> np = dev->of_node; >>>>>>>> >>>>>>>> ? I'm not sure exactly what find_host_bridge() is called, but I'm pretty >>>>>>>> sure that exists. >>>>>>>> >>>>>>>> Once we have that we can still iterate over the iommus property and do >>>>>>>> not need to rely on this global variable. >>>>>>> >>>>>>> I agree that it'd work. But I was hoping to simplify the code >>>>>>> here if it's possible. Looks like we have an argument on this >>>>>>> so I will choose to go with your suggestion above for now. >>>>>> >>>>>> This patch removed more lines than were added. If this will be opposite >>>>>> for the Thierry's suggestion, then it's probably not a great suggestion. >>>>> >>>>> Sorry, I don't quite understand this comments. Would you please >>>>> elaborate what's this "it" being "not a great suggestion"? >>>>> >>>> >>>> I meant that you should try to implement Thierry's solution, but if the >>>> end result will be worse than the current patch, then you shouldn't make >>>> a v4, but get back to this discussion in order to choose the best option >>>> and make everyone agree on it. >>> >>> I see. Thanks for the reply. And here is a sample implementation: >> >> That's what I supposed to happen :) The new variant adds code and >> complexity, while old did the opposite. Hence the old variant is clearly >> more attractive, IMO. > > I personally am not a fan of adding a path for PCI device either, > since PCI/IOMMU cores could have taken care of it while the same > path can't be used for other buses. > > If we can't come to an agreement on globalizing mc pointer, would > it be possible to pass tegra_mc_driver through tegra_smmu_probe() > so we can continue to use driver_find_device_by_fwnode() as v1? > > v1: https://lkml.org/lkml/2020/9/26/68 > I think we already agreed that it will be good to have a common helper. So far Thierry only objected that the implementation of the helper could be improved.
