Re: [RFC PATCH 09/11] drivers: acpi: implement acpi_dma_configure

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

Hi Andy,

On Fri, Apr 22, 2016 at 01:45:38AM +0300, Andy Shevchenko wrote:
> On Thu, Apr 14, 2016 at 8:25 PM, Lorenzo Pieralisi
> <lorenzo.pieralisi@arm.com> wrote:
> > On DT based systems, the of_dma_configure() API implements DMA configuration
> > for a given device. On ACPI systems an API equivalent to of_dma_configure()
> > is missing which implies that it is currently not possible to set-up DMA
> > operations for devices through the ACPI generic kernel layer.
> >
> > This patch fills the gap by introducing acpi_dma_configure/deconfigure()
> > calls, that carry out IOMMU configuration through IORT (on systems where
> > it is present) and call arch_setup_dma_ops(...) with the retrieved
> > parameters.
> >
> > The DMA range size passed to arch_setup_dma_ops() is sized according
> > to the device coherent_dma_mask (starting at address 0x0), mirroring the
> > DT probing path behaviour when a dma-ranges property is not provided
> > for the device being probed; this changes the current arch_setup_dma_ops()
> > call parameters in the ACPI probing case, but since arch_setup_dma_ops()
> > is a NOP on all architectures but ARM/ARM64 this patch does not change
> > the current kernel behaviour on them.
> >
> > This patch updates ACPI and PCI core code to use the newly introduced
> > acpi_dma_configure function, providing the same functionality
> > as of_dma_configure on ARM systems and leaving behaviour unchanged
> > for all other arches.
> >
> 
> Nitpicks below.

Thanks for having a look.

> > --- a/drivers/acpi/iort.c
> > +++ b/drivers/acpi/iort.c
> > @@ -72,6 +72,31 @@ int iort_iommu_set_node(struct iommu_ops *ops, struct acpi_iort_node *node,
> >         return 0;
> >  }
> >
> > +/**
> > + * iort_iommu_get_node - Retrieve iort_iommu_node associated with an IORT node.
> > + *
> > + * @node: IORT table node to be looked-up
> > + *
> > + * Returns: iort_iommu_node pointer on success
> > + *          NULL on failure
> > + */
> > +static struct iort_iommu_node *iort_iommu_get_node(struct acpi_iort_node *node)
> > +{
> > +       struct iort_iommu_node *iommu_node;
> > +
> > +       spin_lock(&iort_iommu_lock);
> > +       list_for_each_entry(iommu_node, &iort_iommu_list, list) {
> > +               if (iommu_node->node == node)
> > +                       goto found;
> > +       }
> > +
> > +       iommu_node = NULL;
> > +found:
> > +       spin_unlock(&iort_iommu_lock);
> > +
> > +       return iommu_node;
> 
> Ouch, and why not to
> 
> strut iommu_node = NULL;
> 
> lock
> list for each() {
>  if ()
>   break;
> }
> unlock
> 
> return iommu_node;

To make sure iommu_node is NULL if no node is found, but this list handling
function needs updating anyway (both locking and list handling), so I will
rework it and take your suggestion into account, I agree it is not that
readable (or safe to begin with).

> ?
> 
> > +}
> 
> 
> > +/**
> > + * iort_iommu_configure - Set-up IOMMU configuration for a device.
> > + *
> > + * @dev: device that requires IOMMU set-up
> > + *
> > + * Returns: iommu_ops pointer on configuration success
> > + *          NULL on configuration failure
> > + */
> > +struct iommu_ops *iort_iommu_configure(struct device *dev)
> > +{
> > +       struct acpi_iort_node *node, *parent;
> > +       struct iommu_ops *ops = NULL;
> > +       struct iommu_fwspec fwspec;
> > +       struct iort_iommu_node *iommu_node;
> > +       u32 rid = 0, devid = 0;
> > +
> > +       if (dev_is_pci(dev)) {
> > +               struct pci_bus *bus = to_pci_dev(dev)->bus;
> > +
> > +               pci_for_each_dma_alias(to_pci_dev(dev), __get_pci_rid,
> > +                                      &rid);
> > +
> > +               node = iort_scan_node(ACPI_IORT_NODE_PCI_ROOT_COMPLEX,
> > +                                     iort_find_dev_callback, &bus->dev);
> 
> > +       } else
> 
> checkpatch.pl ?

checkpatch.pl --strict does not even barf at it. I will add the braces
and go check why checkpatch.pl is quiet :)

> > +               node = iort_scan_node(ACPI_IORT_NODE_NAMED_COMPONENT,
> > +                                     iort_find_dev_callback, dev);
> > +
> > +       if (!node)
> > +               return NULL;
> > +
> > +       iort_dev_map_rid(node, rid, &devid, ACPI_IORT_NODE_SMMU);
> > +
> > +       parent = iort_find_parent_node(node, ACPI_IORT_NODE_SMMU);
> 
> > +
> 
> Redundant.

Ok.

Thanks,
Lorenzo

> 

> > +       if (!parent)
> > +               return NULL;
> > +
> > +       iommu_node = iort_iommu_get_node(parent);
> > +       ops = iommu_node->ops;
> > +
> > +       fwspec.fwnode = iommu_node->fwnode;
> > +       fwspec.param_count = 1;
> > +       fwspec.param[0] = devid;
> > +
> > +       if (!ops || !ops->fw_xlate || ops->fw_xlate(dev, &fwspec))
> > +               return NULL;
> > +
> > +       return ops;
> > +}
> > +
> 
> -- 
> With Best Regards,
> Andy Shevchenko
>