Re: [PATCH] pci: acpi: Generic function for setting up PCI device DMA coherency

[Bjorn Helgaas]

Here it is again.

On Thu, Aug 13, 2015 at 6:50 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote:
> Hi Suravee,
>
> On Thu, Aug 13, 2015 at 04:58:45PM +0700, Suravee Suthikulpanit wrote:
>> This patch refactors of_pci_dma_configure() into a more generic
>> pci_dma_configure(), which can be reused by non-OF code.
>> Then, it adds support for setting up PCI device DMA coherency from
>> ACPI _CCA object that should normally be specified in the DSDT node
>> of its PCI host bridge..
>
> Since this does two things:
>   1) Rename of_pci_dma_configure() and move it to PCI
>   2) Add _CCA support,
> maybe it should be split into two patches?
>
> There are a couple more comments below.
>
> While looking at this, I thought some of the existing code could be
> made simpler and easier to follow.  I appended a couple possible patches;
> you can incorporate them or ignore them, whatever seems best to you.
>
> Bjorn
>
>> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
>> CC: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>> CC: Catalin Marinas <catalin.marinas@xxxxxxx>
>> CC: Will Deacon <will.deacon@xxxxxxx>
>> CC: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>
>> CC: Rob Herring <robh+dt@xxxxxxxxxx>
>> CC: Murali Karicheri <m-karicheri2@xxxxxx>
>> ---
>> Note: According to the ACPI spec, the _CCA attribute is required
>>       for ARM64. Therefore, this patch is a pre-req for ACPI PCI
>>       support for ARM64 which is currently in development.
>>
>>       Also, this should not affect other architectures since
>>       if CCA is not required, the default value is coherent.
>>       Please see include/acpi/acpi_bus.h: acpi_check_dma() and
>>       drivers/acpi/scan.c: acpi_init_coherency() for more information
>>
>>  drivers/of/of_pci.c    | 20 --------------------
>>  drivers/pci/probe.c    | 35 +++++++++++++++++++++++++++++++++--
>>  include/linux/of_pci.h |  3 ---
>>  3 files changed, 33 insertions(+), 25 deletions(-)
>>
>> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
>> index 5751dc5..b66ee4e 100644
>> --- a/drivers/of/of_pci.c
>> +++ b/drivers/of/of_pci.c
>> @@ -117,26 +117,6 @@ int of_get_pci_domain_nr(struct device_node *node)
>>  }
>>  EXPORT_SYMBOL_GPL(of_get_pci_domain_nr);
>>
>> -/**
>> - * of_pci_dma_configure - Setup DMA configuration
>> - * @dev: ptr to pci_dev struct of the PCI device
>> - *
>> - * Function to update PCI devices's DMA configuration using the same
>> - * info from the OF node of host bridge's parent (if any).
>> - */
>> -void of_pci_dma_configure(struct pci_dev *pci_dev)
>> -{
>> -     struct device *dev = &pci_dev->dev;
>> -     struct device *bridge = pci_get_host_bridge_device(pci_dev);
>> -
>> -     if (!bridge->parent)
>> -             return;
>> -
>> -     of_dma_configure(dev, bridge->parent->of_node);
>> -     pci_put_host_bridge_device(bridge);
>> -}
>> -EXPORT_SYMBOL_GPL(of_pci_dma_configure);
>> -
>>  #if defined(CONFIG_OF_ADDRESS)
>>  /**
>>   * of_pci_get_host_bridge_resources - Parse PCI host bridge resources from DT
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index cefd636..e2fcd3b 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -6,12 +6,14 @@
>>  #include <linux/delay.h>
>>  #include <linux/init.h>
>>  #include <linux/pci.h>
>> -#include <linux/of_pci.h>
>> +#include <linux/of_device.h>
>>  #include <linux/pci_hotplug.h>
>>  #include <linux/slab.h>
>>  #include <linux/module.h>
>>  #include <linux/cpumask.h>
>>  #include <linux/pci-aspm.h>
>> +#include <linux/acpi.h>
>> +#include <linux/property.h>
>>  #include <asm-generic/pci-bridge.h>
>>  #include "pci.h"
>>
>> @@ -1544,6 +1546,35 @@ static void pci_init_capabilities(struct pci_dev *dev)
>>       pci_enable_acs(dev);
>>  }
>>
>> +/**
>> + * pci_dma_configure - Setup DMA configuration
>> + * @pci_dev: ptr to pci_dev struct of the PCI device
>> + *
>> + * Function to update PCI devices's DMA configuration using the same
>> + * info from the OF node or ACPI node of host bridge's parent (if any).
>> + */
>> +static void pci_dma_configure(struct pci_dev *pci_dev)
>
> Almost all pci_dev pointers in probe.c are named "dev", so I would use
> that for this one, too.  I probably would just drop the "struct device
> *dev" below and use "&dev->dev" the two places you need it.  That's a
> common idiom in PCI.
>
>> +{
>> +     struct device *dev = &pci_dev->dev;
>> +     struct device *bridge = pci_get_host_bridge_device(pci_dev);
>> +     struct acpi_device *adev;
>> +     bool coherent;
>> +
>> +     if (has_acpi_companion(bridge)) {
>> +             adev = to_acpi_node(bridge->fwnode);
>> +             if (acpi_check_dma(adev, &coherent))
>> +                     arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
>> +     } else {
>> +             struct device *host = bridge->parent;
>> +             if (!host)
>> +                     return;
>> +
>> +             of_dma_configure(dev, host->of_node);
>> +     }
>
> Why is this check reversed with respect to device_dma_is_coherent()?
> In device_dma_is_coherent(), we first look for an OF property, then look
> for ACPI _CCA.  But here we check for _CCA, then for OF.
>
>> +
>> +     pci_put_host_bridge_device(bridge);
>> +}
>> +
>>  void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
>>  {
>>       int ret;
>> @@ -1557,7 +1588,7 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
>>       dev->dev.dma_mask = &dev->dma_mask;
>>       dev->dev.dma_parms = &dev->dma_parms;
>>       dev->dev.coherent_dma_mask = 0xffffffffull;
>> -     of_pci_dma_configure(dev);
>> +     pci_dma_configure(dev);
>>
>>       pci_set_dma_max_seg_size(dev, 65536);
>>       pci_set_dma_seg_boundary(dev, 0xffffffff);
>> diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h
>> index 29fd3fe..ce0e5ab 100644
>> --- a/include/linux/of_pci.h
>> +++ b/include/linux/of_pci.h
>> @@ -16,7 +16,6 @@ int of_pci_get_devfn(struct device_node *np);
>>  int of_irq_parse_and_map_pci(const struct pci_dev *dev, u8 slot, u8 pin);
>>  int of_pci_parse_bus_range(struct device_node *node, struct resource *res);
>>  int of_get_pci_domain_nr(struct device_node *node);
>> -void of_pci_dma_configure(struct pci_dev *pci_dev);
>>  #else
>>  static inline int of_irq_parse_pci(const struct pci_dev *pdev, struct of_phandle_args *out_irq)
>>  {
>> @@ -51,8 +50,6 @@ of_get_pci_domain_nr(struct device_node *node)
>>  {
>>       return -1;
>>  }
>> -
>> -static inline void of_pci_dma_configure(struct pci_dev *pci_dev) { }
>>  #endif
>>
>>  #if defined(CONFIG_OF_ADDRESS)
>> --
>> 2.1.0
>>
> commit 18183957888f601807ca0e166516ae60f682eb62
> Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Date:   Thu Aug 13 20:01:21 2015 -0500
>
>     ACPI / scan: Move _CCA comments to acpi_init_coherency()
>
>     Move the comments about how we handle _CCA to the code that looks at _CCA,
>     and fix a couple typos.
>
>     No functional change.
>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index ec25635..a12e522 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -2188,6 +2188,22 @@ static void acpi_init_coherency(struct acpi_device *adev)
>         acpi_status status;
>         struct acpi_device *parent = adev->parent;
>
> +       /**
> +        * Currently, we only support _CCA=1 (i.e. coherent_dma=1)
> +        * This should be equivalent to specifying dma-coherent for
> +        * a device in OF.
> +        *
> +        * For the case when _CCA=0 (i.e. coherent_dma=0 && cca_seen=1),
> +        * we have two choices:
> +        * case 1. Do not support and disable DMA.
> +        * case 2. Support but rely on arch-specific cache maintenance for
> +        *         non-coherent DMA operations.
> +        * Currently, we implement case 1 above.
> +        *
> +        * For the case when _CCA is missing (i.e. cca_seen=0) and
> +        * platform specifies ACPI_CCA_REQUIRED, we do not support DMA,
> +        * and fallback to arch-specific default handling.
> +        */
>         if (parent && parent->flags.cca_seen) {
>                 /*
>                  * From ACPI spec, OSPM will ignore _CCA if an ancestor
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 83061ca..718942b 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -389,24 +389,6 @@ static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
>         if (!adev)
>                 return ret;
>
> -       /**
> -        * Currently, we only support _CCA=1 (i.e. coherent_dma=1)
> -        * This should be equivalent to specifyig dma-coherent for
> -        * a device in OF.
> -        *
> -        * For the case when _CCA=0 (i.e. coherent_dma=0 && cca_seen=1),
> -        * There are two cases:
> -        * case 1. Do not support and disable DMA.
> -        * case 2. Support but rely on arch-specific cache maintenance for
> -        *         non-coherence DMA operations.
> -        * Currently, we implement case 1 above.
> -        *
> -        * For the case when _CCA is missing (i.e. cca_seen=0) and
> -        * platform specifies ACPI_CCA_REQUIRED, we do not support DMA,
> -        * and fallback to arch-specific default handling.
> -        *
> -        * See acpi_init_coherency() for more info.
> -        */
>         if (adev->flags.coherent_dma) {
>                 ret = true;
>                 if (coherent)
>
> commit 84cfb2213cd400fef227ec0d7829ec4e12895da9
> Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Date:   Thu Aug 13 19:49:52 2015 -0500
>
>     ACPI / scan: Rename acpi_check_dma() to acpi_dma_is_coherent()
>
>     The name "acpi_check_dma()" doesn't give any much indication about what
>     exactly it checks.  The function also returns information both as a normal
>     return value and as the "bool *coherent" return parameter.  But "*coherent"
>     doesn't actually give any extra information: it is unchanged when returning
>     false and set to true when returning true.
>
>     Rename acpi_check_dma() to acpi_dma_is_coherent() so the callers read more
>     naturally.  Drop the return parameter and just use the function return
>     value.
>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
>
> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
> index 06a67d5..fc6138d 100644
> --- a/drivers/acpi/acpi_platform.c
> +++ b/drivers/acpi/acpi_platform.c
> @@ -103,7 +103,7 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
>         pdevinfo.res = resources;
>         pdevinfo.num_res = count;
>         pdevinfo.fwnode = acpi_fwnode_handle(adev);
> -       pdevinfo.dma_mask = acpi_check_dma(adev, NULL) ? DMA_BIT_MASK(32) : 0;
> +       pdevinfo.dma_mask = acpi_dma_is_coherent(adev) ? DMA_BIT_MASK(32) : 0;
>         pdev = platform_device_register_full(&pdevinfo);
>         if (IS_ERR(pdev))
>                 dev_err(&adev->dev, "platform device creation failed: %ld\n",
> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> index b9657af..89b1cf8 100644
> --- a/drivers/acpi/glue.c
> +++ b/drivers/acpi/glue.c
> @@ -168,7 +168,6 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
>         struct list_head *physnode_list;
>         unsigned int node_id;
>         int retval = -EINVAL;
> -       bool coherent;
>
>         if (has_acpi_companion(dev)) {
>                 if (acpi_dev) {
> @@ -225,8 +224,8 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
>         if (!has_acpi_companion(dev))
>                 ACPI_COMPANION_SET(dev, acpi_dev);
>
> -       if (acpi_check_dma(acpi_dev, &coherent))
> -               arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
> +       if (acpi_dma_is_coherent(acpi_dev))
> +               arch_setup_dma_ops(dev, 0, 0, NULL, true);
>
>         acpi_physnode_link_name(physical_node_name, node_id);
>         retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
> diff --git a/drivers/base/property.c b/drivers/base/property.c
> index f3f6d16..1124130 100644
> --- a/drivers/base/property.c
> +++ b/drivers/base/property.c
> @@ -523,13 +523,9 @@ EXPORT_SYMBOL_GPL(device_get_child_node_count);
>
>  bool device_dma_is_coherent(struct device *dev)
>  {
> -       bool coherent = false;
> -
>         if (IS_ENABLED(CONFIG_OF) && dev->of_node)
> -               coherent = of_dma_is_coherent(dev->of_node);
> -       else
> -               acpi_check_dma(ACPI_COMPANION(dev), &coherent);
> +               return of_dma_is_coherent(dev->of_node);
>
> -       return coherent;
> +       return acpi_dma_is_coherent(ACPI_COMPANION(dev));
>  }
>  EXPORT_SYMBOL_GPL(device_dma_is_coherent);
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 718942b..39f1be6 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -382,19 +382,12 @@ struct acpi_device {
>         void (*remove)(struct acpi_device *);
>  };
>
> -static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
> +static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
>  {
> -       bool ret = false;
> +       if (adev && adev->flags.coherent_dma)
> +               return true;
>
> -       if (!adev)
> -               return ret;
> -
> -       if (adev->flags.coherent_dma) {
> -               ret = true;
> -               if (coherent)
> -                       *coherent = adev->flags.coherent_dma;
> -       }
> -       return ret;
> +       return false;
>  }
>
>  static inline bool is_acpi_node(struct fwnode_handle *fwnode)
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index d2445fa..f29b8b5 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -562,7 +562,7 @@ static inline int acpi_device_modalias(struct device *dev,
>         return -ENODEV;
>  }
>
> -static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
> +static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
>  {
>         return false;
>  }
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/