by Andy Shevchenko

[permalink] [raw]

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

On Thu, Apr 14, 2016 at 8:25 PM, Lorenzo Pieralisi
<[email protected]> 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.

> --- 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;

?

> +}

> +/**
> + * 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 ?

> + 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.

> + 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

2016-04-22 10:58:00

by Lorenzo Pieralisi

[permalink] [raw]

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

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
> <[email protected]> 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
>