On Wed, Jan 13, 2021 at 7:48 AM Florian Fainelli <f.fainelli@xxxxxxxxx> wrote:
>
> On 1/5/21 7:41 PM, Claire Chang wrote:
> > If a device is not behind an IOMMU, we look up the device node and set
> > up the restricted DMA when the restricted-dma-pool is presented.
> >
> > Signed-off-by: Claire Chang <tientzu@xxxxxxxxxxxx>
> > ---
>
> [snip]
>
> > +int of_dma_set_restricted_buffer(struct device *dev)
> > +{
> > + struct device_node *node;
> > + int count, i;
> > +
> > + if (!dev->of_node)
> > + return 0;
> > +
> > + count = of_property_count_elems_of_size(dev->of_node, "memory-region",
> > + sizeof(phandle));
>
> You could have an early check for count < 0, along with an error
> message, if that is deemed useful.
>
> > + for (i = 0; i < count; i++) {
> > + node = of_parse_phandle(dev->of_node, "memory-region", i);
> > + if (of_device_is_compatible(node, "restricted-dma-pool"))
>
> And you may want to add here an of_device_is_available(node). A platform
> that provides the Device Tree firmware and try to support multiple
> different SoCs may try to determine if an IOMMU is present, and if it
> is, it could be marking the restriced-dma-pool region with a 'status =
> "disabled"' property, or any variant of that scheme.
This function is called only when there is no IOMMU present (check in
drivers/of/device.c). I can still add of_device_is_available(node)
here if you think it's helpful.
>
> > + return of_reserved_mem_device_init_by_idx(
> > + dev, dev->of_node, i);
>
> This does not seem to be supporting more than one memory region, did not
> you want something like instead:
>
> ret = of_reserved_mem_device_init_by_idx(...);
> if (ret)
> return ret;
>
Yes. This implement only supports one restriced-dma-pool memory region
with the assumption that there is only one memory region with the
compatible string, restricted-dma-pool, in the dts. IIUC, it's similar
to shared-dma-pool.
> > + }
> > +
> > + return 0;
> > +}
> > diff --git a/drivers/of/device.c b/drivers/of/device.c
> > index aedfaaafd3e7..e2c7409956ab 100644
> > --- a/drivers/of/device.c
> > +++ b/drivers/of/device.c
> > @@ -182,6 +182,10 @@ int of_dma_configure_id(struct device *dev, struct device_node *np,
> > arch_setup_dma_ops(dev, dma_start, size, iommu, coherent);
> >
> > dev->dma_range_map = map;
> > +
> > + if (!iommu)
> > + return of_dma_set_restricted_buffer(dev);
> > +
> > return 0;
> > }
> > EXPORT_SYMBOL_GPL(of_dma_configure_id);
> > diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
> > index d9e6a324de0a..28a2dfa197ba 100644
> > --- a/drivers/of/of_private.h
> > +++ b/drivers/of/of_private.h
> > @@ -161,12 +161,17 @@ struct bus_dma_region;
> > #if defined(CONFIG_OF_ADDRESS) && defined(CONFIG_HAS_DMA)
> > int of_dma_get_range(struct device_node *np,
> > const struct bus_dma_region **map);
> > +int of_dma_set_restricted_buffer(struct device *dev);
> > #else
> > static inline int of_dma_get_range(struct device_node *np,
> > const struct bus_dma_region **map)
> > {
> > return -ENODEV;
> > }
> > +static inline int of_dma_get_restricted_buffer(struct device *dev)
> > +{
> > + return -ENODEV;
> > +}
> > #endif
> >
> > #endif /* _LINUX_OF_PRIVATE_H */
> >
>
>
> --
> Florian
