Re: [RFC PATCH] of: Fix DMA configuration for non-DT masters

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On Wed, Mar 29, 2017 at 10:23 AM, Oza Oza <oza.oza@xxxxxxxxxxxx> wrote:
> On Wed, Mar 29, 2017 at 12:27 AM, Robin Murphy <robin.murphy@xxxxxxx> wrote:
>> For PCI masters not represented in DT, we pass the OF node of their
>> associated host bridge to of_dma_configure(), such that they can inherit
>> the appropriate DMA configuration from whatever is described there.
>> Unfortunately, whilst this has worked for the "dma-coherent" property,
>> it turns out to miss the case where the host bridge node has a non-empty
>> "dma-ranges", since nobody is expecting the 'device' to be a bus itself.
>>
>> It transpires, though, that the de-facto interface since the prototype
>> change in 1f5c69aa51f9 ("of: Move of_dma_configure() to device.c to help
>> re-use") is very clear-cut: either the master_np argument is redundant
>> with dev->of_node, or dev->of_node is NULL and master_np is the relevant
>> parent bus. Let's ratify that behaviour, then teach the whole
>> of_dma_configure() pipeline to cope with both cases properly.
>>
>> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
>> ---
>>
>> This is what I'd consider the better fix - rather than adding yet more
>> special cases - which will also make it simple to handle multiple
>> "dma-ranges" entries with minimal further disruption. The callers now
>> left passing dev->of_node as 'parent' are harmless, but look a bit silly
>> and clearly want cleaning up - I'd be partial to renaming the existing
>> function and having a single-argument wrapper for the 'normal' case, e.g.:
>>
>> static inline int of_dma_configure(struct device_node *dev)
>> {
>>         return of_dma_configure_parent(dev, NULL);
>> }
>>
>> Thoughts?
>>
>> Robin.
>>
>>  drivers/iommu/of_iommu.c   |  7 ++++---
>>  drivers/of/address.c       | 37 +++++++++++++++++++++++++------------
>>  drivers/of/device.c        | 12 +++++++-----
>>  include/linux/of_address.h |  7 ++++---
>>  include/linux/of_device.h  |  4 ++--
>>  include/linux/of_iommu.h   |  4 ++--
>>  6 files changed, 44 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
>> index 2683e9fc0dcf..35aff07bb5eb 100644
>> --- a/drivers/iommu/of_iommu.c
>> +++ b/drivers/iommu/of_iommu.c
>> @@ -138,21 +138,22 @@ static const struct iommu_ops
>>  }
>>
>>  const struct iommu_ops *of_iommu_configure(struct device *dev,
>> -                                          struct device_node *master_np)
>> +                                          struct device_node *parent)
>>  {
>>         struct of_phandle_args iommu_spec;
>> -       struct device_node *np;
>> +       struct device_node *np, *master_np;
>>         const struct iommu_ops *ops = NULL;
>>         int idx = 0;
>>
>>         if (dev_is_pci(dev))
>> -               return of_pci_iommu_configure(to_pci_dev(dev), master_np);
>> +               return of_pci_iommu_configure(to_pci_dev(dev), parent);
>>
>>         /*
>>          * We don't currently walk up the tree looking for a parent IOMMU.
>>          * See the `Notes:' section of
>>          * Documentation/devicetree/bindings/iommu/iommu.txt
>>          */
>> +       master_np = dev->of_node ? dev->of_node : parent;
>>         while (!of_parse_phandle_with_args(master_np, "iommus",
>>                                            "#iommu-cells", idx,
>>                                            &iommu_spec)) {
>> diff --git a/drivers/of/address.c b/drivers/of/address.c
>> index 02b2903fe9d2..833bc17f5e55 100644
>> --- a/drivers/of/address.c
>> +++ b/drivers/of/address.c
>> @@ -808,6 +808,7 @@ EXPORT_SYMBOL(of_io_request_and_map);
>>  /**
>>   * of_dma_get_range - Get DMA range info
>>   * @np:                device node to get DMA range info
>> + * @parent:    node of device's parent bus, if @np is NULL
>>   * @dma_addr:  pointer to store initial DMA address of DMA range
>>   * @paddr:     pointer to store initial CPU address of DMA range
>>   * @size:      pointer to store size of DMA range
>> @@ -822,36 +823,48 @@ EXPORT_SYMBOL(of_io_request_and_map);
>>   * It returns -ENODEV if "dma-ranges" property was not found
>>   * for this device in DT.
>>   */
>> -int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *size)
>> +int of_dma_get_range(struct device_node *np, struct device_node *parent,
>> +                    u64 *dma_addr, u64 *paddr, u64 *size)
>>  {
>> -       struct device_node *node = of_node_get(np);
>> +       struct device_node *node;
>>         const __be32 *ranges = NULL;
>>         int len, naddr, nsize, pna;
>>         int ret = 0;
>>         u64 dmaaddr;
>>
>> -       if (!node)
>> -               return -EINVAL;
>> -
>> -       while (1) {
>> +       if (np) {
>> +               node = of_node_get(np);
>>                 naddr = of_n_addr_cells(node);
>>                 nsize = of_n_size_cells(node);
>>                 node = of_get_next_parent(node);
>> -               if (!node)
>> -                       break;
>> +       } else if (parent) {
>> +               node = of_node_get(parent);
>> +               np = parent;
>> +               if (of_property_read_u32(node, "#address-cells", &naddr))
>> +                       naddr = of_n_addr_cells(node);
>> +               if (of_property_read_u32(node, "#size-cells", &nsize))
>> +                       nsize = of_n_size_cells(node);
>> +       } else {
>> +               return -EINVAL;
>> +       }
>>
>> +       while (node) {
>>                 ranges = of_get_property(node, "dma-ranges", &len);
>>
>> -               /* Ignore empty ranges, they imply no translation required */
>> -               if (ranges && len > 0)
>> -                       break;
>> -
>>                 /*
>>                  * At least empty ranges has to be defined for parent node if
>>                  * DMA is supported
>>                  */
>>                 if (!ranges)
>>                         break;
>> +
>> +               /* Ignore empty ranges, they imply no translation required */
>> +               if (len > 0)
>> +                       break;
>> +
>> +               naddr = of_n_addr_cells(node);
>> +               nsize = of_n_size_cells(node);
>> +               node = of_get_next_parent(node);
>>         }
>>
>>         if (!ranges) {
>> diff --git a/drivers/of/device.c b/drivers/of/device.c
>> index 9bb8518b28f2..57ec5324ed6c 100644
>> --- a/drivers/of/device.c
>> +++ b/drivers/of/device.c
>> @@ -73,7 +73,8 @@ int of_device_add(struct platform_device *ofdev)
>>  /**
>>   * of_dma_configure - Setup DMA configuration
>>   * @dev:       Device to apply DMA configuration
>> - * @np:                Pointer to OF node having DMA configuration
>> + * @parent:    OF node of device's parent bus, if @dev is not
>> + *             represented in DT (i.e. @dev->of_node is NULL)
>>   *
>>   * Try to get devices's DMA configuration from DT and update it
>>   * accordingly.
>> @@ -82,13 +83,14 @@ int of_device_add(struct platform_device *ofdev)
>>   * can use a platform bus notifier and handle BUS_NOTIFY_ADD_DEVICE events
>>   * to fix up DMA configuration.
>>   */
>> -void of_dma_configure(struct device *dev, struct device_node *np)
>> +void of_dma_configure(struct device *dev, struct device_node *parent)
>>  {
>>         u64 dma_addr, paddr, size;
>>         int ret;
>>         bool coherent;
>>         unsigned long offset;
>>         const struct iommu_ops *iommu;
>> +       struct device_node *np = dev->of_node;
>>
>>         /*
>>          * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
>> @@ -104,7 +106,7 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>>         if (!dev->dma_mask)
>>                 dev->dma_mask = &dev->coherent_dma_mask;
>>
>> -       ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
>> +       ret = of_dma_get_range(np, parent, &dma_addr, &paddr, &size);
>>         if (ret < 0) {
>>                 dma_addr = offset = 0;
>>                 size = dev->coherent_dma_mask + 1;
>> @@ -132,11 +134,11 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>>         dev->coherent_dma_mask = DMA_BIT_MASK(ilog2(dma_addr + size));
>>         *dev->dma_mask = dev->coherent_dma_mask;
>>
>> -       coherent = of_dma_is_coherent(np);
>> +       coherent = of_dma_is_coherent(np ? np : parent);
>>         dev_dbg(dev, "device is%sdma coherent\n",
>>                 coherent ? " " : " not ");
>>
>> -       iommu = of_iommu_configure(dev, np);
>> +       iommu = of_iommu_configure(dev, parent);
>>         dev_dbg(dev, "device is%sbehind an iommu\n",
>>                 iommu ? " " : " not ");
>>
>> diff --git a/include/linux/of_address.h b/include/linux/of_address.h
>> index 37864734ca50..f1a507f3ae57 100644
>> --- a/include/linux/of_address.h
>> +++ b/include/linux/of_address.h
>> @@ -52,8 +52,8 @@ extern int of_pci_range_parser_init(struct of_pci_range_parser *parser,
>>  extern struct of_pci_range *of_pci_range_parser_one(
>>                                         struct of_pci_range_parser *parser,
>>                                         struct of_pci_range *range);
>> -extern int of_dma_get_range(struct device_node *np, u64 *dma_addr,
>> -                               u64 *paddr, u64 *size);
>> +extern int of_dma_get_range(struct device_node *np, struct device_node *parent,
>> +                               u64 *dma_addr, u64 *paddr, u64 *size);
>>  extern bool of_dma_is_coherent(struct device_node *np);
>>  #else /* CONFIG_OF_ADDRESS */
>>  static inline void __iomem *of_io_request_and_map(struct device_node *device,
>> @@ -95,7 +95,8 @@ static inline struct of_pci_range *of_pci_range_parser_one(
>>         return NULL;
>>  }
>>
>> -static inline int of_dma_get_range(struct device_node *np, u64 *dma_addr,
>> +static inline int of_dma_get_range(struct device_node *np,
>> +                               struct device_node *parent, u64 *dma_addr,
>>                                 u64 *paddr, u64 *size)
>>  {
>>         return -ENODEV;
>> diff --git a/include/linux/of_device.h b/include/linux/of_device.h
>> index c12dace043f3..bcd2b6fbeef3 100644
>> --- a/include/linux/of_device.h
>> +++ b/include/linux/of_device.h
>> @@ -55,7 +55,7 @@ static inline struct device_node *of_cpu_device_node_get(int cpu)
>>         return of_node_get(cpu_dev->of_node);
>>  }
>>
>> -void of_dma_configure(struct device *dev, struct device_node *np);
>> +void of_dma_configure(struct device *dev, struct device_node *parent);
>>  #else /* CONFIG_OF */
>>
>>  static inline int of_driver_match_device(struct device *dev,
>> @@ -103,7 +103,7 @@ static inline struct device_node *of_cpu_device_node_get(int cpu)
>>  {
>>         return NULL;
>>  }
>> -static inline void of_dma_configure(struct device *dev, struct device_node *np)
>> +static inline void of_dma_configure(struct device *dev, struct device_node *parent)
>>  {}
>>  #endif /* CONFIG_OF */
>>
>> diff --git a/include/linux/of_iommu.h b/include/linux/of_iommu.h
>> index 13394ac83c66..c02b62e8e6ed 100644
>> --- a/include/linux/of_iommu.h
>> +++ b/include/linux/of_iommu.h
>> @@ -12,7 +12,7 @@ extern int of_get_dma_window(struct device_node *dn, const char *prefix,
>>                              size_t *size);
>>
>>  extern const struct iommu_ops *of_iommu_configure(struct device *dev,
>> -                                       struct device_node *master_np);
>> +                                       struct device_node *parent);
>>
>>  #else
>>
>> @@ -24,7 +24,7 @@ static inline int of_get_dma_window(struct device_node *dn, const char *prefix,
>>  }
>>
>>  static inline const struct iommu_ops *of_iommu_configure(struct device *dev,
>> -                                        struct device_node *master_np)
>> +                                        struct device_node *parent)
>>  {
>>         return NULL;
>>  }
>> --
>> 2.11.0.dirty
>>
>
> pci and memory mapped device world is different. of course if you talk
> from iommu perspective, all the master are same for IOMMU
>
> but the original intention of the patch is to try to solve 2 problems.
> please refer to https://lkml.org/lkml/2017/3/29/10
>
> 1) expose generic API for pci world clients to configure their
> dma-ranges. right now there is none.
> 2) same API can be used by IOMMU to derive dma_mask.
>
> while the current patch posted to handle dma-ranges for both memory
> mapped and pci devices, which I think is overdoing.
>
> besides we have different configuration of dma-ranges based on iommu
> is enabled or not enabled.
>  #define PCIE_DMA_RANGES dma-ranges = <0x43000000 0x00 0x80000000 0x00
> 0x80000000 0x00 0x80000000 \
>                                       0x43000000 0x08 0x00000000 0x08
> 0x00000000 0x08 0x00000000 \
>                                       0x43000000 0x80 0x00000000 0x80
> 0x00000000 0x40 0x00000000>;
> Not sure if this patch will consider above dma-ranges.
>
> my suggestion is to leave existing of_dma_get_range as is, and have
> new function for pci world as discussed in
> please refer to https://lkml.org/lkml/2017/3/29/10
>
> Regards,
> Oza.

also I see that, in case of multiple ranges of_dma_get_range doesnt handle that.
and also it is not meant to handle.
so with this patch will return wrong size and hence wrong dma_mask.
having said, I think it is better to separate pci world dma-ranges
function on of_pci.c

for which my discussion with Rob already, (same thread)
https://lkml.org/lkml/2017/3/29/10
Waiting for Rob's viewpoint on this.


Regards,
Oza.
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