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SubjectRe: [RFC PATCH 1/4] bus: fsl-mc: add custom .dma_configure implementation
On Thu, Feb 27, 2020 at 12:05:39PM +0200, laurentiu.tudor@nxp.com wrote:
> From: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>
> 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@nxp.com>
> ---
> 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 - the streamid are injected directly here
bypassing OF/IORT bindings translations altogether. Am I reading this
code correctly ?

Thanks,
Lorenzo

> + 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
>

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