Hi Lorenzo, On 3/25/2020 2:51 PM, Lorenzo Pieralisi wrote: > On Thu, Feb 27, 2020 at 12:05:39PM +0200, laurentiu.tudor@xxxxxxx wrote: >> From: Laurentiu Tudor <laurentiu.tudor@xxxxxxx> >> >> The devices on this bus are not discovered by way of device tree >> but by queries to the firmware. It makes little sense to trick the >> generic of layer into thinking that these devices are of related so >> that we can get our dma configuration. Instead of doing that, add >> our custom dma configuration implementation. >> >> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx> >> --- >> drivers/bus/fsl-mc/fsl-mc-bus.c | 31 ++++++++++++++++++++++++++++++- >> 1 file changed, 30 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c >> index 36eb25f82c8e..eafaa0e0b906 100644 >> --- a/drivers/bus/fsl-mc/fsl-mc-bus.c >> +++ b/drivers/bus/fsl-mc/fsl-mc-bus.c >> @@ -132,11 +132,40 @@ static int fsl_mc_bus_uevent(struct device *dev, struct kobj_uevent_env *env) >> static int fsl_mc_dma_configure(struct device *dev) >> { >> struct device *dma_dev = dev; >> + struct iommu_fwspec *fwspec; >> + const struct iommu_ops *iommu_ops; >> + struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev); >> + int ret; >> + u32 icid; >> >> while (dev_is_fsl_mc(dma_dev)) >> dma_dev = dma_dev->parent; >> >> - return of_dma_configure(dev, dma_dev->of_node, 0); >> + fwspec = dev_iommu_fwspec_get(dma_dev); >> + if (!fwspec) >> + return -ENODEV; >> + iommu_ops = iommu_ops_from_fwnode(fwspec->iommu_fwnode); >> + if (!iommu_ops) >> + return -ENODEV; >> + >> + ret = iommu_fwspec_init(dev, fwspec->iommu_fwnode, iommu_ops); >> + if (ret) >> + return ret; >> + >> + icid = mc_dev->icid; >> + ret = iommu_fwspec_add_ids(dev, &icid, 1); > > I see. So with this patch we would use the MC named component only to > retrieve the iommu_ops Right. I'd also add that the implementation tries to follow the existing standard .dma_configure implementations, e.g. of_dma_configure + of_iommu_configure. I'd also note that similarly to the ACPI case, this MC FW device is probed as a platform device in the DT scenario, binding here [1]. A similar approach is used for the retrieval of the msi irq domain, see following patch. > - the streamid are injected directly here bypassing OF/IORT bindings translations altogether. Actually I've submitted a v2 [2] that calls into .of_xlate() to allow the smmu driver to do some processing on the raw streamid coming from the firmware. I have not yet tested this with ACPI but expect it to work, however, it's debatable how valid is this approach in the context of ACPI. > Am I reading this code correctly ? Yes. Thanks for taking the time. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt [2] https://www.spinics.net/lists/arm-kernel/msg794757.html --- Best Regards, Laurentiu > >> + if (ret) >> + return ret; >> + >> + if (!device_iommu_mapped(dev)) { >> + ret = iommu_probe_device(dev); >> + if (ret) >> + return ret; >> + } >> + >> + arch_setup_dma_ops(dev, 0, *dma_dev->dma_mask + 1, iommu_ops, true); >> + >> + return 0; >> } >> >> static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, >> -- >> 2.17.1 >>