Hi Robin/Lorenzo, >Hi Robin,Lorenzo, > >>On Wed, Nov 30, 2016 at 04:42:27PM +0000, Robin Murphy wrote: >>> On 30/11/16 16:17, Lorenzo Pieralisi wrote: >>> > Sricharan, Robin, >>> > >>> > I gave this series a go on ACPI and apart from an SMMU v3 fix-up >>> > it seems to work, more thorough testing required though. >>> > >>> > A key question below. >>> > >>> > On Wed, Nov 30, 2016 at 05:52:16AM +0530, Sricharan R wrote: >>> >> From: Robin Murphy <robin.murphy@xxxxxxx> >>> >> >>> >> IOMMU configuration represents unchanging properties of the hardware, >>> >> and as such should only need happen once in a device's lifetime, but >>> >> the necessary interaction with the IOMMU device and driver complicates >>> >> exactly when that point should be. >>> >> >>> >> Since the only reasonable tool available for handling the inter-device >>> >> dependency is probe deferral, we need to prepare of_iommu_configure() >>> >> to run later than it is currently called (i.e. at driver probe rather >>> >> than device creation), to handle being retried, and to tell whether a >>> >> not-yet present IOMMU should be waited for or skipped (by virtue of >>> >> having declared a built-in driver or not). >>> >> >>> >> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx> >>> >> --- >>> >> drivers/iommu/of_iommu.c | 30 +++++++++++++++++++++++++++++- >>> >> 1 file changed, 29 insertions(+), 1 deletion(-) >>> >> >>> >> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c >>> >> index ee49081..349bd1d 100644 >>> >> --- a/drivers/iommu/of_iommu.c >>> >> +++ b/drivers/iommu/of_iommu.c >>> >> @@ -104,12 +104,20 @@ int of_get_dma_window(struct device_node *dn, const char *prefix, int index, >>> >> int err; >>> >> >>> >> ops = iommu_get_instance(fwnode); >>> >> - if (!ops || !ops->of_xlate) >>> >> + if ((ops && !ops->of_xlate) || >>> >> + (!ops && !of_match_node(&__iommu_of_table, iommu_spec->np))) >>> > >>> > IIUC of_match_node() here is there to check there is a driver compiled >>> > in for this device_node (aka compatible string in OF world), correct ? >>> >>> Yes - specifically, it's checking the magic table for a matching >>> IOMMU_OF_DECLARE entry. >>> >>> > If that's the case (and I think that's what Sricharan was referring to >>> > in his ACPI query) I need to cook-up something on the ACPI side to >>> > emulate the OF linker table behaviour (or anyway to detect a driver is >>> > actually in the kernel), it is not that difficult but it is key to know, >>> > I will give it some thought to make it as clean as possible. >>> >>> I didn't think this would be a concern for ACPI, since IORT works much >>> the same way the current of_iommu_init_fn/of_platform_device_create() >>> bodges in drivers so for DT. If you can only discover SMMUs from IORT, >>> then iort_init_platform_devices() will have already created every SMMU >>> that's going to exist before discovering other devices from wherever >>> they come from, thus you could never get into the situation of probing a >>> device without its SMMU being ready (if it's ever going to be). Is that >>> not right? >> >>It is right, my point and question is: we are probing a device and we >>have to know whether it is worth deferring its IOMMU DMA setup. On DT, >>through of_match_node(&__iommu_of_table, iommu_device_node) we check at >>once that: >> >>1 - A device for the IOMMU exists >> >>AND >> >>2 - A driver for the IOMMU is compiled in the kernel >> >>Is this correct ? As you said (1) is not a concern on ACPI IORT (because >>we create the IOMMU device before _any_ other device so either the IOMMU >>device is there or it will never be by the time master devices are >>probed), but for (2) I need to slightly change how the IORT linker entry >>work to make sure we can detect a driver is actually compiled in the >>kernel, it is easy, I was just asking if my understanding was correct >>and I think that was what Sricharan was referring to in his query. >> > >Yes right, this was what i was looking for in the ACPI case and putting this >in the iort_iommu_xlate was needed to return EPROBE_DEFER when the >driver is not yet been probed. With the thinking of taking this series through, would it be fine if i cleanup the pci configure hanging outside and push it in to of/acpi_iommu configure respectively ? This time with all neeeded for ACPI added as well. Also on the last post of V4, Lorenzo commented that it worked for him, although still the of_match_node equivalent in ACPI has to be added. If i can get that, then i will add that as well to make this complete. Regards, Sricharan -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
