Messages in this thread | | | Subject | Re: [PATCH v7 3/3] iommu/tegra-smmu: Add PCI support | From | Robin Murphy <> | Date | Fri, 16 Oct 2020 15:10:26 +0100 |
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On 2020-10-16 04:53, Nicolin Chen wrote: > On Thu, Oct 15, 2020 at 10:55:52AM +0100, Robin Murphy wrote: >> On 2020-10-15 05:13, Nicolin Chen wrote: >>> On Wed, Oct 14, 2020 at 06:42:36PM +0100, Robin Murphy wrote: >>>> On 2020-10-09 17:19, Nicolin Chen wrote: >>>>> This patch simply adds support for PCI devices. >>>>> >>>>> Reviewed-by: Dmitry Osipenko <digetx@gmail.com> >>>>> Tested-by: Dmitry Osipenko <digetx@gmail.com> >>>>> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com> >>>>> --- >>>>> >>>>> Changelog >>>>> v6->v7 >>>>> * Renamed goto labels, suggested by Thierry. >>>>> v5->v6 >>>>> * Added Dmitry's Reviewed-by and Tested-by. >>>>> v4->v5 >>>>> * Added Dmitry's Reviewed-by >>>>> v3->v4 >>>>> * Dropped !iommu_present() check >>>>> * Added CONFIG_PCI check in the exit path >>>>> v2->v3 >>>>> * Replaced ternary conditional operator with if-else in .device_group() >>>>> * Dropped change in tegra_smmu_remove() >>>>> v1->v2 >>>>> * Added error-out labels in tegra_smmu_probe() >>>>> * Dropped pci_request_acs() since IOMMU core would call it. >>>>> >>>>> drivers/iommu/tegra-smmu.c | 35 +++++++++++++++++++++++++---------- >>>>> 1 file changed, 25 insertions(+), 10 deletions(-) >>>>> >>>>> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c >>>>> index be29f5977145..2941d6459076 100644 >>>>> --- a/drivers/iommu/tegra-smmu.c >>>>> +++ b/drivers/iommu/tegra-smmu.c >>>>> @@ -10,6 +10,7 @@ >>>>> #include <linux/kernel.h> >>>>> #include <linux/of.h> >>>>> #include <linux/of_device.h> >>>>> +#include <linux/pci.h> >>>>> #include <linux/platform_device.h> >>>>> #include <linux/slab.h> >>>>> #include <linux/spinlock.h> >>>>> @@ -865,7 +866,11 @@ static struct iommu_group *tegra_smmu_device_group(struct device *dev) >>>>> group->smmu = smmu; >>>>> group->soc = soc; >>>>> - group->group = iommu_group_alloc(); >>>>> + if (dev_is_pci(dev)) >>>>> + group->group = pci_device_group(dev); >>>> >>>> Just to check, is it OK to have two or more swgroups "owning" the same >>>> iommu_group if an existing one gets returned here? It looks like that might >>>> not play nice with the use of iommu_group_set_iommudata(). >>> >>> Do you mean by "gets returned here" the "IS_ERR" check below? >> >> I mean that unlike iommu_group_alloc()/generic_device_group(), >> pci_device_group() may give you back a group that already contains another >> device and has already been set up from that device's perspective. This can >> happen for topological reasons like requester ID aliasing through a PCI-PCIe >> bridge or lack of isolation between functions. > > Okay..but we don't really have two swgroups owning the same groups > in case of PCI devices. For Tegra210, all PCI devices inherit the > same swgroup from the PCI controller. And I'd think previous chips > do the same. The only use case currently of 2+ swgroups owning the > same iommu_group is for display controller. > > Or do you suggest we need an additional check for pci_device_group?
Ah, OK - I still don't have the best comprehension of what exactly swgroups are, and the path through .of_xlate looked like you might be using the PCI requester ID as the swgroup identifier, but I guess that ultimately depends on what your "iommu-map" is supposed to look like. If pci_device_group() will effectively only ever get called once regardless of how many endpoints exist, then indeed this won't be a concern (although if that's *guaranteed* to be the case then you may as well just stick with calling iommu_group_alloc() directly). Thanks for clarifying.
Robin.
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