[1/2] OF/PCI: Export inbound memory interface to PCI RC drivers.

Commit Message

Marek Vasut Aug. 9, 2019, 5:34 p.m. UTC

From: Oza Pawandeep <[e-mail]>

The patch exports interface to PCIe RC drivers so that,
Drivers can get their inbound memory configuration.

It provides basis for IOVA reservations for inbound memory
holes, if RC is not capable of addressing all the host memory,
Specifically when IOMMU is enabled and on ARMv8 where 64bit IOVA
could be allocated.

It handles multiple inbound windows, and returns resources,
and is left to the caller, how it wants to use them.

Signed-off-by: Oza Pawandeep <[e-mail]>
Signed-off-by: Marek Vasut <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Cc: Geert Uytterhoeven <[e-mail]>
Cc: Lorenzo Pieralisi <[e-mail]>
Cc: Robin Murphy <[e-mail]>
Cc: Simon Horman <[e-mail]>
Cc: Wolfram Sang <[e-mail]>
Cc: [e-mail]
To: [e-mail]
---
 drivers/pci/of.c       | 96 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/of_pci.h |  7 +++
 2 files changed, 103 insertions(+)

Comments

Simon Horman Aug. 9, 2019, 8:56 p.m. UTC | #1

On Fri, Aug 09, 2019 at 07:34:48PM +0200, [e-mail] wrote:
> From: Oza Pawandeep <[e-mail]>
> 
> The patch exports interface to PCIe RC drivers so that,
> Drivers can get their inbound memory configuration.
> 
> It provides basis for IOVA reservations for inbound memory
> holes, if RC is not capable of addressing all the host memory,
> Specifically when IOMMU is enabled and on ARMv8 where 64bit IOVA
> could be allocated.
> 
> It handles multiple inbound windows, and returns resources,
> and is left to the caller, how it wants to use them.
> 
> Signed-off-by: Oza Pawandeep <[e-mail]>
> Signed-off-by: Marek Vasut <[e-mail]>
> Cc: Arnd Bergmann <[e-mail]>
> Cc: Geert Uytterhoeven <[e-mail]>
> Cc: Lorenzo Pieralisi <[e-mail]>
> Cc: Robin Murphy <[e-mail]>
> Cc: Simon Horman <[e-mail]>
> Cc: Wolfram Sang <[e-mail]>
> Cc: [e-mail]
> To: [e-mail]
> ---
>  drivers/pci/of.c       | 96 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_pci.h |  7 +++
>  2 files changed, 103 insertions(+)
> 
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index bc7b27a28795..4018f1a26f6f 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -347,6 +347,102 @@ int devm_of_pci_get_host_bridge_resources(struct device *dev,
>  	return err;
>  }
>  EXPORT_SYMBOL_GPL(devm_of_pci_get_host_bridge_resources);
> +
> +/**
> + * of_pci_get_dma_ranges - Parse PCI host bridge inbound resources from DT
> + * @np: device node of the host bridge having the dma-ranges property
> + * @resources: list where the range of resources will be added after DT parsing
> + *
> + * It is the caller's job to free the @resources list.
> + *
> + * This function will parse the "dma-ranges" property of a
> + * PCI host bridge device node and setup the resource mapping based
> + * on its content.
> + *
> + * It returns zero if the range parsing has been successful or a standard error
> + * value if it failed.
> + */
> +
> +int of_pci_get_dma_ranges(struct device_node *dn, struct list_head *resources)
> +{
> +	struct device_node *node = of_node_get(dn);
> +	int rlen;
> +	int pna = of_n_addr_cells(node);
> +	const int na = 3, ns = 2;
> +	int np = pna + na + ns;
> +	int ret = 0;
> +	struct resource *res;
> +	const u32 *dma_ranges;

It seems that const __be32 * would be a more appropriate type
for dma_ranges as that seems to be the expected type in
all uses below.

> +	struct of_pci_range range;
> +
> +	if (!node)
> +		return -EINVAL;
> +
> +	while (1) {
> +		dma_ranges = of_get_property(node, "dma-ranges", &rlen);
> +
> +		/* Ignore empty ranges, they imply no translation required. */
> +		if (dma_ranges && rlen > 0)
> +			break;
> +
> +		/* no dma-ranges, they imply no translation required. */
> +		if (!dma_ranges)
> +			break;
> +
> +		node = of_get_next_parent(node);
> +
> +		if (!node)
> +			break;
> +	}
> +
> +	if (!dma_ranges) {
> +		pr_debug("pcie device has no dma-ranges defined for node(%s)\n",
> +			  dn->full_name);
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	while ((rlen -= np * 4) >= 0) {
> +		range.pci_space = be32_to_cpup((const __be32 *) &dma_ranges[0]);

	Can &dma_ranges[0] be more succinctly written as dma_ranges ?

> +		range.pci_addr = of_read_number(dma_ranges + 1, ns);
> +		range.cpu_addr = of_translate_dma_address(node,
> +							dma_ranges + na);
> +		range.size = of_read_number(dma_ranges + pna + na, ns);
> +		range.flags = IORESOURCE_MEM;
> +
> +		dma_ranges += np;
> +
> +		/*
> +		 * If we failed translation or got a zero-sized region
> +		 * then skip this range.
> +		 */
> +		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
> +			continue;
> +
> +		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> +		if (!res) {
> +			ret = -ENOMEM;
> +			goto parse_failed;
> +		}
> +
> +		ret = of_pci_range_to_resource(&range, dn, res);
> +		if (ret) {
> +			kfree(res);
> +			continue;
> +		}
> +
> +		pci_add_resource_offset(resources, res,
> +					res->start - range.pci_addr);
> +	}
> +	return ret;
> +
> +parse_failed:
> +	pci_free_resource_list(resources);
> +out:
> +	of_node_put(node);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(of_pci_get_dma_ranges);
>  #endif /* CONFIG_OF_ADDRESS */
>  
>  #if IS_ENABLED(CONFIG_OF_IRQ)
> diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
> index 21a89c4880fa..02bff0587dd2 100644
> --- a/include/linux/of_pci.h
> +++ b/include/linux/of_pci.h
> @@ -13,6 +13,7 @@ struct device_node;
>  struct device_node *of_pci_find_child_device(struct device_node *parent,
>  					     unsigned int devfn);
>  int of_pci_get_devfn(struct device_node *np);
> +int of_pci_get_dma_ranges(struct device_node *np, struct list_head *resources);
>  void of_pci_check_probe_only(void);
>  #else
>  static inline struct device_node *of_pci_find_child_device(struct device_node *parent,
> @@ -26,6 +27,12 @@ static inline int of_pci_get_devfn(struct device_node *np)
>  	return -EINVAL;
>  }
>  
> +static inline int of_pci_get_dma_ranges(struct device_node *np,
> +					struct list_head *resources)
> +{
> +	return -EINVAL;
> +}
> +
>  static inline void of_pci_check_probe_only(void) { }
>  #endif
>  
> -- 
> 2.20.1
>

Marek Vasut Aug. 9, 2019, 9:22 p.m. UTC | #2

On 8/9/19 10:56 PM, Simon Horman wrote:
> On Fri, Aug 09, 2019 at 07:34:48PM +0200, [e-mail] wrote:
>> From: Oza Pawandeep <[e-mail]>
>>
>> The patch exports interface to PCIe RC drivers so that,
>> Drivers can get their inbound memory configuration.
>>
>> It provides basis for IOVA reservations for inbound memory
>> holes, if RC is not capable of addressing all the host memory,
>> Specifically when IOMMU is enabled and on ARMv8 where 64bit IOVA
>> could be allocated.
>>
>> It handles multiple inbound windows, and returns resources,
>> and is left to the caller, how it wants to use them.
>>
>> Signed-off-by: Oza Pawandeep <[e-mail]>
>> Signed-off-by: Marek Vasut <[e-mail]>
>> Cc: Arnd Bergmann <[e-mail]>
>> Cc: Geert Uytterhoeven <[e-mail]>
>> Cc: Lorenzo Pieralisi <[e-mail]>
>> Cc: Robin Murphy <[e-mail]>
>> Cc: Simon Horman <[e-mail]>
>> Cc: Wolfram Sang <[e-mail]>
>> Cc: [e-mail]
>> To: [e-mail]
>> ---
>>  drivers/pci/of.c       | 96 ++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/of_pci.h |  7 +++
>>  2 files changed, 103 insertions(+)
>>
>> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
>> index bc7b27a28795..4018f1a26f6f 100644
>> --- a/drivers/pci/of.c
>> +++ b/drivers/pci/of.c
>> @@ -347,6 +347,102 @@ int devm_of_pci_get_host_bridge_resources(struct device *dev,
>>  	return err;
>>  }
>>  EXPORT_SYMBOL_GPL(devm_of_pci_get_host_bridge_resources);
>> +
>> +/**
>> + * of_pci_get_dma_ranges - Parse PCI host bridge inbound resources from DT
>> + * @np: device node of the host bridge having the dma-ranges property
>> + * @resources: list where the range of resources will be added after DT parsing
>> + *
>> + * It is the caller's job to free the @resources list.
>> + *
>> + * This function will parse the "dma-ranges" property of a
>> + * PCI host bridge device node and setup the resource mapping based
>> + * on its content.
>> + *
>> + * It returns zero if the range parsing has been successful or a standard error
>> + * value if it failed.
>> + */
>> +
>> +int of_pci_get_dma_ranges(struct device_node *dn, struct list_head *resources)
>> +{
>> +	struct device_node *node = of_node_get(dn);
>> +	int rlen;
>> +	int pna = of_n_addr_cells(node);
>> +	const int na = 3, ns = 2;
>> +	int np = pna + na + ns;
>> +	int ret = 0;
>> +	struct resource *res;
>> +	const u32 *dma_ranges;
> 
> It seems that const __be32 * would be a more appropriate type
> for dma_ranges as that seems to be the expected type in
> all uses below.

Noted, but I'm more interested in some conceptual input about this --
whether this is the right approach or not.

Seems like we now have iMX8, R-Car3 and some Broadcom SoCs affected by
this issue, with no solution in sight for years, so I think something
has to be done here.

Bjorn Helgaas Sept. 30, 2019, 9:40 p.m. UTC | #3

This would follow the convention for subject lines:

  PCI: OF: Add of_pci_get_dma_ranges() for inbound DMA restrictions

On Fri, Aug 09, 2019 at 07:34:48PM +0200, [e-mail] wrote:
> From: Oza Pawandeep <[e-mail]>
> 
> The patch exports interface to PCIe RC drivers so that,
> Drivers can get their inbound memory configuration.

IIUC this interface (of_pci_get_dma_ranges()) is not used directly by
*drivers*; it is used by of_bus_pci_get_dma_ranges() in the next
patch, and it's called by the driver core via this path:

  really_probe
    pci_dma_configure                     # pci_bus_type.dma_configure
      of_dma_configure
	of_dma_get_range
	  bus->get_dma_ranges
	    of_bus_pci_get_dma_ranges     # of_busses[0].get_dma_ranges
	      of_pci_get_dma_ranges

> It provides basis for IOVA reservations for inbound memory
> holes, if RC is not capable of addressing all the host memory,
> Specifically when IOMMU is enabled and on ARMv8 where 64bit IOVA
> could be allocated.
> 
> It handles multiple inbound windows, and returns resources,
> and is left to the caller, how it wants to use them.

This should say exactly what the problem is, maybe even with a link to
a problem report.  I assume it is something like "RC <X> cannot
address all of host memory, and if we happen to allocate a buffer
that's not addressable, DMA to the buffer fails".  It'd be nice to
know what the failure looks like (SERR# asserted, panic, reboot, etc).

> Signed-off-by: Oza Pawandeep <[e-mail]>
> Signed-off-by: Marek Vasut <[e-mail]>
> Cc: Arnd Bergmann <[e-mail]>
> Cc: Geert Uytterhoeven <[e-mail]>
> Cc: Lorenzo Pieralisi <[e-mail]>
> Cc: Robin Murphy <[e-mail]>
> Cc: Simon Horman <[e-mail]>
> Cc: Wolfram Sang <[e-mail]>
> Cc: [e-mail]
> To: [e-mail]
> ---
>  drivers/pci/of.c       | 96 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/of_pci.h |  7 +++
>  2 files changed, 103 insertions(+)
> 
> diff --git a/drivers/pci/of.c b/drivers/pci/of.c
> index bc7b27a28795..4018f1a26f6f 100644
> --- a/drivers/pci/of.c
> +++ b/drivers/pci/of.c
> @@ -347,6 +347,102 @@ int devm_of_pci_get_host_bridge_resources(struct device *dev,
>  	return err;
>  }
>  EXPORT_SYMBOL_GPL(devm_of_pci_get_host_bridge_resources);
> +
> +/**
> + * of_pci_get_dma_ranges - Parse PCI host bridge inbound resources from DT
> + * @np: device node of the host bridge having the dma-ranges property
> + * @resources: list where the range of resources will be added after DT parsing
> + *
> + * It is the caller's job to free the @resources list.
> + *
> + * This function will parse the "dma-ranges" property of a
> + * PCI host bridge device node and setup the resource mapping based
> + * on its content.

Rewrap this so it uses the whole width (75-78 columns).

> + * It returns zero if the range parsing has been successful or a standard error
> + * value if it failed.
> + */
> +
> +int of_pci_get_dma_ranges(struct device_node *dn, struct list_head *resources)
> +{
> +	struct device_node *node = of_node_get(dn);
> +	int rlen;
> +	int pna = of_n_addr_cells(node);
> +	const int na = 3, ns = 2;
> +	int np = pna + na + ns;
> +	int ret = 0;
> +	struct resource *res;
> +	const u32 *dma_ranges;
> +	struct of_pci_range range;
> +
> +	if (!node)
> +		return -EINVAL;
> +
> +	while (1) {
> +		dma_ranges = of_get_property(node, "dma-ranges", &rlen);
> +
> +		/* Ignore empty ranges, they imply no translation required. */
> +		if (dma_ranges && rlen > 0)
> +			break;
> +
> +		/* no dma-ranges, they imply no translation required. */

Capitalize as you do other comments (s/no/No/).

> +		if (!dma_ranges)
> +			break;
> +
> +		node = of_get_next_parent(node);
> +
> +		if (!node)
> +			break;
> +	}
> +
> +	if (!dma_ranges) {
> +		pr_debug("pcie device has no dma-ranges defined for node(%s)\n",

This isn't PCIe-specific, so it should say "PCI".

> +			  dn->full_name);
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	while ((rlen -= np * 4) >= 0) {
> +		range.pci_space = be32_to_cpup((const __be32 *) &dma_ranges[0]);
> +		range.pci_addr = of_read_number(dma_ranges + 1, ns);
> +		range.cpu_addr = of_translate_dma_address(node,
> +							dma_ranges + na);
> +		range.size = of_read_number(dma_ranges + pna + na, ns);
> +		range.flags = IORESOURCE_MEM;
> +
> +		dma_ranges += np;
> +
> +		/*
> +		 * If we failed translation or got a zero-sized region
> +		 * then skip this range.
> +		 */
> +		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
> +			continue;
> +
> +		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> +		if (!res) {
> +			ret = -ENOMEM;
> +			goto parse_failed;
> +		}
> +
> +		ret = of_pci_range_to_resource(&range, dn, res);
> +		if (ret) {
> +			kfree(res);
> +			continue;
> +		}
> +
> +		pci_add_resource_offset(resources, res,
> +					res->start - range.pci_addr);
> +	}
> +	return ret;
> +
> +parse_failed:
> +	pci_free_resource_list(resources);
> +out:
> +	of_node_put(node);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(of_pci_get_dma_ranges);

I don't think this needs to be exported, does it?  The only caller I
see (of_bus_pci_get_dma_ranges()) cannot be in a module.

>  #endif /* CONFIG_OF_ADDRESS */
>  
>  #if IS_ENABLED(CONFIG_OF_IRQ)
> diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
> index 21a89c4880fa..02bff0587dd2 100644
> --- a/include/linux/of_pci.h
> +++ b/include/linux/of_pci.h
> @@ -13,6 +13,7 @@ struct device_node;
>  struct device_node *of_pci_find_child_device(struct device_node *parent,
>  					     unsigned int devfn);
>  int of_pci_get_devfn(struct device_node *np);
> +int of_pci_get_dma_ranges(struct device_node *np, struct list_head *resources);
>  void of_pci_check_probe_only(void);
>  #else
>  static inline struct device_node *of_pci_find_child_device(struct device_node *parent,
> @@ -26,6 +27,12 @@ static inline int of_pci_get_devfn(struct device_node *np)
>  	return -EINVAL;
>  }
>  
> +static inline int of_pci_get_dma_ranges(struct device_node *np,
> +					struct list_head *resources)
> +{
> +	return -EINVAL;
> +}
> +
>  static inline void of_pci_check_probe_only(void) { }
>  #endif
>  
> -- 
> 2.20.1
>

Marek Vasut Sept. 30, 2019, 9:46 p.m. UTC | #4

On 9/30/19 11:40 PM, Bjorn Helgaas wrote:
> This would follow the convention for subject lines:
> 
>   PCI: OF: Add of_pci_get_dma_ranges() for inbound DMA restrictions
> 
> On Fri, Aug 09, 2019 at 07:34:48PM +0200 wrote:
>> From: Oza Pawandeep
>>
>> The patch exports interface to PCIe RC drivers so that,
>> Drivers can get their inbound memory configuration.
> 
> IIUC this interface (of_pci_get_dma_ranges()) is not used directly by
> *drivers*; it is used by of_bus_pci_get_dma_ranges() in the next
> patch, and it's called by the driver core via this path:
> 
>   really_probe
>     pci_dma_configure                     # pci_bus_type.dma_configure
>       of_dma_configure
> 	of_dma_get_range
> 	  bus->get_dma_ranges
> 	    of_bus_pci_get_dma_ranges     # of_busses[0].get_dma_ranges
> 	      of_pci_get_dma_ranges
> 
>> It provides basis for IOVA reservations for inbound memory
>> holes, if RC is not capable of addressing all the host memory,
>> Specifically when IOMMU is enabled and on ARMv8 where 64bit IOVA
>> could be allocated.
>>
>> It handles multiple inbound windows, and returns resources,
>> and is left to the caller, how it wants to use them.
> 
> This should say exactly what the problem is, maybe even with a link to
> a problem report.  I assume it is something like "RC <X> cannot
> address all of host memory, and if we happen to allocate a buffer
> that's not addressable, DMA to the buffer fails".  It'd be nice to
> know what the failure looks like (SERR# asserted, panic, reboot, etc).

[...]

While it's good that someone finally looked at these patches, these were
since superseded by the following series:
https://patchwork.ozlabs.org/cover/1168166/

Bjorn Helgaas Oct. 1, 2019, 12:27 p.m. UTC | #5

[-cc Oza, bounced]

On Mon, Sep 30, 2019 at 11:46:18PM +0200, Marek Vasut wrote:
> On 9/30/19 11:40 PM, Bjorn Helgaas wrote:
> > This would follow the convention for subject lines:
> > 
> >   PCI: OF: Add of_pci_get_dma_ranges() for inbound DMA restrictions
> > 
> > On Fri, Aug 09, 2019 at 07:34:48PM +0200 wrote:
> >> From: Oza Pawandeep
> >>
> >> The patch exports interface to PCIe RC drivers so that,
> >> Drivers can get their inbound memory configuration.
> > 
> > IIUC this interface (of_pci_get_dma_ranges()) is not used directly by
> > *drivers*; it is used by of_bus_pci_get_dma_ranges() in the next
> > patch, and it's called by the driver core via this path:
> > 
> >   really_probe
> >     pci_dma_configure                     # pci_bus_type.dma_configure
> >       of_dma_configure
> > 	of_dma_get_range
> > 	  bus->get_dma_ranges
> > 	    of_bus_pci_get_dma_ranges     # of_busses[0].get_dma_ranges
> > 	      of_pci_get_dma_ranges
> > 
> >> It provides basis for IOVA reservations for inbound memory
> >> holes, if RC is not capable of addressing all the host memory,
> >> Specifically when IOMMU is enabled and on ARMv8 where 64bit IOVA
> >> could be allocated.
> >>
> >> It handles multiple inbound windows, and returns resources,
> >> and is left to the caller, how it wants to use them.
> > 
> > This should say exactly what the problem is, maybe even with a link to
> > a problem report.  I assume it is something like "RC <X> cannot
> > address all of host memory, and if we happen to allocate a buffer
> > that's not addressable, DMA to the buffer fails".  It'd be nice to
> > know what the failure looks like (SERR# asserted, panic, reboot, etc).
> 
> [...]
> 
> While it's good that someone finally looked at these patches, these were
> since superseded by the following series:
> https://patchwork.ozlabs.org/cover/1168166/

Good to know, thanks :)

Patch

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index bc7b27a28795..4018f1a26f6f 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -347,6 +347,102 @@  int devm_of_pci_get_host_bridge_resources(struct device *dev,
 	return err;
 }
 EXPORT_SYMBOL_GPL(devm_of_pci_get_host_bridge_resources);
+
+/**
+ * of_pci_get_dma_ranges - Parse PCI host bridge inbound resources from DT
+ * @np: device node of the host bridge having the dma-ranges property
+ * @resources: list where the range of resources will be added after DT parsing
+ *
+ * It is the caller's job to free the @resources list.
+ *
+ * This function will parse the "dma-ranges" property of a
+ * PCI host bridge device node and setup the resource mapping based
+ * on its content.
+ *
+ * It returns zero if the range parsing has been successful or a standard error
+ * value if it failed.
+ */
+
+int of_pci_get_dma_ranges(struct device_node *dn, struct list_head *resources)
+{
+	struct device_node *node = of_node_get(dn);
+	int rlen;
+	int pna = of_n_addr_cells(node);
+	const int na = 3, ns = 2;
+	int np = pna + na + ns;
+	int ret = 0;
+	struct resource *res;
+	const u32 *dma_ranges;
+	struct of_pci_range range;
+
+	if (!node)
+		return -EINVAL;
+
+	while (1) {
+		dma_ranges = of_get_property(node, "dma-ranges", &rlen);
+
+		/* Ignore empty ranges, they imply no translation required. */
+		if (dma_ranges && rlen > 0)
+			break;
+
+		/* no dma-ranges, they imply no translation required. */
+		if (!dma_ranges)
+			break;
+
+		node = of_get_next_parent(node);
+
+		if (!node)
+			break;
+	}
+
+	if (!dma_ranges) {
+		pr_debug("pcie device has no dma-ranges defined for node(%s)\n",
+			  dn->full_name);
+		ret = -EINVAL;
+		goto out;
+	}
+
+	while ((rlen -= np * 4) >= 0) {
+		range.pci_space = be32_to_cpup((const __be32 *) &dma_ranges[0]);
+		range.pci_addr = of_read_number(dma_ranges + 1, ns);
+		range.cpu_addr = of_translate_dma_address(node,
+							dma_ranges + na);
+		range.size = of_read_number(dma_ranges + pna + na, ns);
+		range.flags = IORESOURCE_MEM;
+
+		dma_ranges += np;
+
+		/*
+		 * If we failed translation or got a zero-sized region
+		 * then skip this range.
+		 */
+		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
+			continue;
+
+		res = kzalloc(sizeof(struct resource), GFP_KERNEL);
+		if (!res) {
+			ret = -ENOMEM;
+			goto parse_failed;
+		}
+
+		ret = of_pci_range_to_resource(&range, dn, res);
+		if (ret) {
+			kfree(res);
+			continue;
+		}
+
+		pci_add_resource_offset(resources, res,
+					res->start - range.pci_addr);
+	}
+	return ret;
+
+parse_failed:
+	pci_free_resource_list(resources);
+out:
+	of_node_put(node);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(of_pci_get_dma_ranges);
 #endif /* CONFIG_OF_ADDRESS */
 
 #if IS_ENABLED(CONFIG_OF_IRQ)
diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
index 21a89c4880fa..02bff0587dd2 100644
--- a/include/linux/of_pci.h
+++ b/include/linux/of_pci.h
@@ -13,6 +13,7 @@  struct device_node;
 struct device_node *of_pci_find_child_device(struct device_node *parent,
 					     unsigned int devfn);
 int of_pci_get_devfn(struct device_node *np);
+int of_pci_get_dma_ranges(struct device_node *np, struct list_head *resources);
 void of_pci_check_probe_only(void);
 #else
 static inline struct device_node *of_pci_find_child_device(struct device_node *parent,
@@ -26,6 +27,12 @@  static inline int of_pci_get_devfn(struct device_node *np)
 	return -EINVAL;
 }
 
+static inline int of_pci_get_dma_ranges(struct device_node *np,
+					struct list_head *resources)
+{
+	return -EINVAL;
+}
+
 static inline void of_pci_check_probe_only(void) { }
 #endif