[V2,1/5] ACPI / scan: Parse _CCA and setup device coherency

Commit Message

Suravee Suthikulpanit May 5, 2015, 3:12 p.m. UTC

This patch implements support for ACPI _CCA object, which is introduced in
ACPIv5.1, can be used for specifying device DMA coherency attribute.

The parsing logic traverses device namespace to parse coherency
information, and stores it in acpi_device_flags. Then uses it to call
arch_setup_dma_ops() when creating each device enumerated in DSDT
during ACPI scan.

This patch also introduces acpi_dma_is_coherent(), which provides
an interface for device drivers to check the coherency information
similarly to the of_dma_is_coherent().

Signed-off-by: Mark Salter <[e-mail]>
Signed-off-by: Suravee Suthikulpanit <[e-mail]>
---
NOTE:
 * Since there seem to be conflict opinions regarding how
   architecture should handle _CCA=0. So, I am proposing the
   CONFIG_ARCH_SUPPORT_CCA_ZERO, which can be specified by
   for each architecture to define behavior of the ACPI
   scanning code when _CCA=0. Let me know if this is acceptable.

 drivers/acpi/Kconfig         |  6 +++++
 drivers/acpi/acpi_platform.c |  4 ++-
 drivers/acpi/scan.c          | 62 ++++++++++++++++++++++++++++++++++++++++++++
 include/acpi/acpi_bus.h      | 11 +++++++-
 include/linux/acpi.h         |  5 ++++
 5 files changed, 86 insertions(+), 2 deletions(-)

Comments

Rafael J. Wysocki May 5, 2015, 8:36 p.m. UTC | #1

On Tuesday, May 05, 2015 10:12:05 AM Suravee Suthikulpanit wrote:
> This patch implements support for ACPI _CCA object, which is introduced in
> ACPIv5.1, can be used for specifying device DMA coherency attribute.
> 
> The parsing logic traverses device namespace to parse coherency
> information, and stores it in acpi_device_flags. Then uses it to call
> arch_setup_dma_ops() when creating each device enumerated in DSDT
> during ACPI scan.
> 
> This patch also introduces acpi_dma_is_coherent(), which provides
> an interface for device drivers to check the coherency information
> similarly to the of_dma_is_coherent().
> 
> Signed-off-by: Mark Salter <[e-mail]>
> Signed-off-by: Suravee Suthikulpanit <[e-mail]>
> ---
> NOTE:
>  * Since there seem to be conflict opinions regarding how
>    architecture should handle _CCA=0. So, I am proposing the
>    CONFIG_ARCH_SUPPORT_CCA_ZERO, which can be specified by
>    for each architecture to define behavior of the ACPI
>    scanning code when _CCA=0. Let me know if this is acceptable.
> 
>  drivers/acpi/Kconfig         |  6 +++++
>  drivers/acpi/acpi_platform.c |  4 ++-
>  drivers/acpi/scan.c          | 62 ++++++++++++++++++++++++++++++++++++++++++++
>  include/acpi/acpi_bus.h      | 11 +++++++-
>  include/linux/acpi.h         |  5 ++++
>  5 files changed, 86 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index ab2cbb5..dd386e9 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -54,6 +54,12 @@ config ACPI_GENERIC_GSI
>  config ACPI_SYSTEM_POWER_STATES_SUPPORT
>  	bool
>  
> +config ACPI_MUST_HAVE_CCA

ACPI_CCA_REQUIRED maybe?

> +	bool
> +
> +config ACPI_SUPPORT_CCA_ZERO

I guess this means "we support devices that can DMA, but are not coherent".
right?

> +	bool
> +
>  config ACPI_SLEEP
>  	bool
>  	depends on SUSPEND || HIBERNATION
> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
> index 4bf7559..a6feca4 100644
> --- a/drivers/acpi/acpi_platform.c
> +++ b/drivers/acpi/acpi_platform.c
> @@ -108,9 +108,11 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
>  	if (IS_ERR(pdev))
>  		dev_err(&adev->dev, "platform device creation failed: %ld\n",
>  			PTR_ERR(pdev));
> -	else
> +	else {

Please add braces to both branches when making such changes (as per CodingStyle).

> +		acpi_setup_device_dma(adev, &pdev->dev);

Why do we need to do that here (for the second time)?

>  		dev_dbg(&adev->dev, "created platform device %s\n",
>  			dev_name(&pdev->dev));
> +	}
>  
>  	kfree(resources);
>  	return pdev;
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 849b699..ac33b29 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -11,6 +11,7 @@
>  #include <linux/kthread.h>
>  #include <linux/dmi.h>
>  #include <linux/nls.h>
> +#include <linux/dma-mapping.h>
>  
>  #include <asm/pgtable.h>
>  
> @@ -2137,6 +2138,66 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
>  	kfree(pnp->unique_id);
>  }
>  
> +void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev)
> +{
> +	int coherent = acpi_dma_is_coherent(adev);
> +
> +	/**
> +	 * Currently, we only support DMA for devices that _CCA=1
> +	 * since this seems to be the case on most ACPI platforms.
> +	 *
> +	 * For the case when _CCA=0 (i.e. is_coherent=0 && cca_seen=1),
> +	 * we would rely on arch-specific cache maintenance for
> +	 * non-coherence DMA operations if architecture enables
> +	 * CONFIG_ACPI_SUPPORT_CCA_ZERO.
> +	 *
> +	 * For the case when _CCA is missing but platform requires it
> +	 * (i.e. is_coherent=0 && cca_seen=0), we do not call
> +	 * arch_setup_dma_ops() and fallback to arch-specific default
> +	 * handling.
> +	 */
> +	if (adev->flags.cca_seen) {
> +		if (!coherent && !IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
> +			return;
> +		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);

Oh dear.

What about

	if (adev->flags.cca_seen && (coherent || IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO)))
		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);

I wonder how this is going to affect x86/ia64 too?

> +	}
> +}
> +
> +static void acpi_init_coherency(struct acpi_device *adev)
> +{
> +	unsigned long long cca = 0;
> +	acpi_status status;
> +	struct acpi_device *parent = adev->parent;
> +
> +	if (parent && parent->flags.cca_seen) {
> +		/*
> +		 * From ACPI spec, OSPM will ignore _CCA if an ancestor
> +		 * already saw one.
> +		 */
> +		adev->flags.cca_seen = 1;
> +		cca = acpi_dma_is_coherent(parent);
> +	} else {
> +		status = acpi_evaluate_integer(adev->handle, "_CCA",
> +					       NULL, &cca);
> +		if (ACPI_SUCCESS(status)) {
> +			adev->flags.cca_seen = 1;
> +		} else if (!IS_ENABLED(CONFIG_ACPI_MUST_HAVE_CCA)) {
> +			/*
> +			 * If architecture does not specify that _CCA is
> +			 * required for DMA-able devices (e.g. x86),
> +			 * we default to _CCA=1.
> +			 */
> +			cca = 1;
> +		} else {
> +			dev_err(&adev->dev, FW_BUG
> +				"DMA is not setup due to missing _CCA.\n");
> +		}
> +	}
> +
> +	adev->flags.is_coherent = cca;
> +	acpi_setup_device_dma(adev, &adev->dev);
> +}
> +
>  void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
>  			     int type, unsigned long long sta)
>  {
> @@ -2155,6 +2216,7 @@ void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
>  	device->flags.visited = false;
>  	device_initialize(&device->dev);
>  	dev_set_uevent_suppress(&device->dev, true);
> +	acpi_init_coherency(device);
>  }
>  
>  void acpi_device_add_finalize(struct acpi_device *device)
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 8de4fa9..b804183 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -208,7 +208,9 @@ struct acpi_device_flags {
>  	u32 visited:1;
>  	u32 hotplug_notify:1;
>  	u32 is_dock_station:1;
> -	u32 reserved:23;
> +	u32 is_coherent:1;
> +	u32 cca_seen:1;
> +	u32 reserved:21;

That will conflict with a patch I've already queued up, but never mind.

>  };
>  
>  /* File System */
> @@ -380,6 +382,13 @@ struct acpi_device {
>  	void (*remove)(struct acpi_device *);
>  };
>  
> +static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
> +{
> +	return adev && adev->flags.is_coherent;
> +}
> +
> +void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev);
> +
>  static inline bool is_acpi_node(struct fwnode_handle *fwnode)
>  {
>  	return fwnode && fwnode->type == FWNODE_ACPI;
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index b10c4a6..d14e777 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -583,6 +583,11 @@ static inline int acpi_device_modalias(struct device *dev,
>  	return -ENODEV;
>  }
>  
> +static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
> +{
> +	return false;
> +}
> +
>  #define ACPI_PTR(_ptr)	(NULL)
>  
>  #endif	/* !CONFIG_ACPI */
>

Hanjun Guo May 6, 2015, 3:13 a.m. UTC | #2

On 2015?05?05? 23:12, Suravee Suthikulpanit wrote:
> This patch implements support for ACPI _CCA object, which is introduced in
> ACPIv5.1, can be used for specifying device DMA coherency attribute.
>
> The parsing logic traverses device namespace to parse coherency
> information, and stores it in acpi_device_flags. Then uses it to call
> arch_setup_dma_ops() when creating each device enumerated in DSDT
> during ACPI scan.
>
> This patch also introduces acpi_dma_is_coherent(), which provides
> an interface for device drivers to check the coherency information
> similarly to the of_dma_is_coherent().
>
> Signed-off-by: Mark Salter <[e-mail]>
> Signed-off-by: Suravee Suthikulpanit <[e-mail]>
> ---
> NOTE:
>   * Since there seem to be conflict opinions regarding how
>     architecture should handle _CCA=0. So, I am proposing the
>     CONFIG_ARCH_SUPPORT_CCA_ZERO, which can be specified by
>     for each architecture to define behavior of the ACPI
>     scanning code when _CCA=0. Let me know if this is acceptable.
>
>   drivers/acpi/Kconfig         |  6 +++++
>   drivers/acpi/acpi_platform.c |  4 ++-
>   drivers/acpi/scan.c          | 62 ++++++++++++++++++++++++++++++++++++++++++++
>   include/acpi/acpi_bus.h      | 11 +++++++-
>   include/linux/acpi.h         |  5 ++++
>   5 files changed, 86 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index ab2cbb5..dd386e9 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -54,6 +54,12 @@ config ACPI_GENERIC_GSI
>   config ACPI_SYSTEM_POWER_STATES_SUPPORT
>   	bool
>
> +config ACPI_MUST_HAVE_CCA
> +	bool
> +
> +config ACPI_SUPPORT_CCA_ZERO
> +	bool
> +
>   config ACPI_SLEEP
>   	bool
>   	depends on SUSPEND || HIBERNATION
> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
> index 4bf7559..a6feca4 100644
> --- a/drivers/acpi/acpi_platform.c
> +++ b/drivers/acpi/acpi_platform.c
> @@ -108,9 +108,11 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
>   	if (IS_ERR(pdev))
>   		dev_err(&adev->dev, "platform device creation failed: %ld\n",
>   			PTR_ERR(pdev));
> -	else
> +	else {
> +		acpi_setup_device_dma(adev, &pdev->dev);
>   		dev_dbg(&adev->dev, "created platform device %s\n",
>   			dev_name(&pdev->dev));
> +	}
>
>   	kfree(resources);
>   	return pdev;
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 849b699..ac33b29 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -11,6 +11,7 @@
>   #include <linux/kthread.h>
>   #include <linux/dmi.h>
>   #include <linux/nls.h>
> +#include <linux/dma-mapping.h>
>
>   #include <asm/pgtable.h>
>
> @@ -2137,6 +2138,66 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
>   	kfree(pnp->unique_id);
>   }
>
> +void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev)

I aasume adev->dev in struct *adev is the same as struct device *dev
passed here, so

> +{
> +	int coherent = acpi_dma_is_coherent(adev);
> +
> +	/**
> +	 * Currently, we only support DMA for devices that _CCA=1
> +	 * since this seems to be the case on most ACPI platforms.
> +	 *
> +	 * For the case when _CCA=0 (i.e. is_coherent=0 && cca_seen=1),
> +	 * we would rely on arch-specific cache maintenance for
> +	 * non-coherence DMA operations if architecture enables
> +	 * CONFIG_ACPI_SUPPORT_CCA_ZERO.
> +	 *
> +	 * For the case when _CCA is missing but platform requires it
> +	 * (i.e. is_coherent=0 && cca_seen=0), we do not call
> +	 * arch_setup_dma_ops() and fallback to arch-specific default
> +	 * handling.
> +	 */
> +	if (adev->flags.cca_seen) {
> +		if (!coherent && !IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
> +			return;
> +		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);

how about using &adev->dev here, and just pass struct acpi_device *adev
for this function?

Thanks
Hanjun

Suravee Suthikulpanit May 6, 2015, 4:15 a.m. UTC | #3

[RESEND]

On 5/5/15 15:36, Rafael J. Wysocki wrote:
> On Tuesday, May 05, 2015 10:12:05 AM Suravee Suthikulpanit wrote:
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index ab2cbb5..dd386e9 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -54,6 +54,12 @@ config ACPI_GENERIC_GSI
>>   config ACPI_SYSTEM_POWER_STATES_SUPPORT
>>   	bool
>>
>> +config ACPI_MUST_HAVE_CCA
>
> ACPI_CCA_REQUIRED maybe?

Sure.

>
>> +	bool
>> +
>> +config ACPI_SUPPORT_CCA_ZERO
>
> I guess this means "we support devices that can DMA, but are not coherent".
> right?

Yes, basically when _CCA=0.

>> +	bool
>> +
>>   config ACPI_SLEEP
>>   	bool
>>   	depends on SUSPEND || HIBERNATION
>> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
>> index 4bf7559..a6feca4 100644
>> --- a/drivers/acpi/acpi_platform.c
>> +++ b/drivers/acpi/acpi_platform.c
>> @@ -108,9 +108,11 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
>>   	if (IS_ERR(pdev))
>>   		dev_err(&adev->dev, "platform device creation failed: %ld\n",
>>   			PTR_ERR(pdev));
>> -	else
>> +	else {
>
> Please add braces to both branches when making such changes (as per CodingStyle).
>

OK.

>> +		acpi_setup_device_dma(adev, &pdev->dev);
>
> Why do we need to do that here (for the second time)?

Because we are calling:
   acpi_create_platform_device()
     |--> platform_device_register_device_full()
       |-->platform_device_alloc()

This creates platform_device, which allocate a new platform_device->dev. 
This is not the same as the original acpi_device->dev that was created 
during acpi_add_single_object(). So, we have to set up the device 
coherency again.


>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 849b699..ac33b29 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/kthread.h>
>>   #include <linux/dmi.h>
>>   #include <linux/nls.h>
>> +#include <linux/dma-mapping.h>
>>
>>   #include <asm/pgtable.h>
>>
>> @@ -2137,6 +2138,66 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
>>   	kfree(pnp->unique_id);
>>   }
>>
>> +void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev)
>> +{
>> +	int coherent = acpi_dma_is_coherent(adev);
>> +
>> +	/**
>> +	 * Currently, we only support DMA for devices that _CCA=1
>> +	 * since this seems to be the case on most ACPI platforms.
>> +	 *
>> +	 * For the case when _CCA=0 (i.e. is_coherent=0 && cca_seen=1),
>> +	 * we would rely on arch-specific cache maintenance for
>> +	 * non-coherence DMA operations if architecture enables
>> +	 * CONFIG_ACPI_SUPPORT_CCA_ZERO.
>> +	 *
>> +	 * For the case when _CCA is missing but platform requires it
>> +	 * (i.e. is_coherent=0 && cca_seen=0), we do not call
>> +	 * arch_setup_dma_ops() and fallback to arch-specific default
>> +	 * handling.
>> +	 */
>> +	if (adev->flags.cca_seen) {
>> +		if (!coherent && !IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
>> +			return;
>> +		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
>
> Oh dear.

I made a mistake here. This logic should also call arch_setup_dma_ops() 
when cca_seen=0 and coherent=1 (e.g. when _CCA is not required and 
default to coherent when it is missing). The current logic doesn't do that.

>
> What about
>
> 	if (adev->flags.cca_seen && (coherent || IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO)))
> 		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);

What about:
	if (coherent ||
	    (adev->flags.cca_seen &&
			IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
	
> I wonder how this is going to affect x86/ia64 too?
>

This should not affect x86 since arch_setup_dma_ops() is currently not 
implement for x86, and default to NOP (see include/linux/dma-mapping.h). 
  Also, on x86, _CCA is not required and default to 1 if missing.

Thanks,

Suravee

Suravee Suthikulpanit May 6, 2015, 4:17 a.m. UTC | #4

On 5/5/15 22:13, Hanjun Guo wrote:
> On 2015?05?05? 23:12, Suravee Suthikulpanit wrote:
>> This patch implements support for ACPI _CCA object, which is
>> introduced in
>> ACPIv5.1, can be used for specifying device DMA coherency attribute.
>>
>> The parsing logic traverses device namespace to parse coherency
>> information, and stores it in acpi_device_flags. Then uses it to call
>> arch_setup_dma_ops() when creating each device enumerated in DSDT
>> during ACPI scan.
>>
>> This patch also introduces acpi_dma_is_coherent(), which provides
>> an interface for device drivers to check the coherency information
>> similarly to the of_dma_is_coherent().
>>
>> Signed-off-by: Mark Salter <[e-mail]>
>> Signed-off-by: Suravee Suthikulpanit <[e-mail]>
>> ---
>> NOTE:
>>   * Since there seem to be conflict opinions regarding how
>>     architecture should handle _CCA=0. So, I am proposing the
>>     CONFIG_ARCH_SUPPORT_CCA_ZERO, which can be specified by
>>     for each architecture to define behavior of the ACPI
>>     scanning code when _CCA=0. Let me know if this is acceptable.
>>
>>   drivers/acpi/Kconfig         |  6 +++++
>>   drivers/acpi/acpi_platform.c |  4 ++-
>>   drivers/acpi/scan.c          | 62
>> ++++++++++++++++++++++++++++++++++++++++++++
>>   include/acpi/acpi_bus.h      | 11 +++++++-
>>   include/linux/acpi.h         |  5 ++++
>>   5 files changed, 86 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index ab2cbb5..dd386e9 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -54,6 +54,12 @@ config ACPI_GENERIC_GSI
>>   config ACPI_SYSTEM_POWER_STATES_SUPPORT
>>       bool
>>
>> +config ACPI_MUST_HAVE_CCA
>> +    bool
>> +
>> +config ACPI_SUPPORT_CCA_ZERO
>> +    bool
>> +
>>   config ACPI_SLEEP
>>       bool
>>       depends on SUSPEND || HIBERNATION
>> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
>> index 4bf7559..a6feca4 100644
>> --- a/drivers/acpi/acpi_platform.c
>> +++ b/drivers/acpi/acpi_platform.c
>> @@ -108,9 +108,11 @@ struct platform_device
>> *acpi_create_platform_device(struct acpi_device *adev)
>>       if (IS_ERR(pdev))
>>           dev_err(&adev->dev, "platform device creation failed: %ld\n",
>>               PTR_ERR(pdev));
>> -    else
>> +    else {
>> +        acpi_setup_device_dma(adev, &pdev->dev);
>>           dev_dbg(&adev->dev, "created platform device %s\n",
>>               dev_name(&pdev->dev));
>> +    }
>>
>>       kfree(resources);
>>       return pdev;
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 849b699..ac33b29 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -11,6 +11,7 @@
>>   #include <linux/kthread.h>
>>   #include <linux/dmi.h>
>>   #include <linux/nls.h>
>> +#include <linux/dma-mapping.h>
>>
>>   #include <asm/pgtable.h>
>>
>> @@ -2137,6 +2138,66 @@ void acpi_free_pnp_ids(struct acpi_device_pnp
>> *pnp)
>>       kfree(pnp->unique_id);
>>   }
>>
>> +void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev)
>
> I aasume adev->dev in struct *adev is the same as struct device *dev
> passed here, so
>
>> +{
>> +    int coherent = acpi_dma_is_coherent(adev);
>> +
>> +    /**
>> +     * Currently, we only support DMA for devices that _CCA=1
>> +     * since this seems to be the case on most ACPI platforms.
>> +     *
>> +     * For the case when _CCA=0 (i.e. is_coherent=0 && cca_seen=1),
>> +     * we would rely on arch-specific cache maintenance for
>> +     * non-coherence DMA operations if architecture enables
>> +     * CONFIG_ACPI_SUPPORT_CCA_ZERO.
>> +     *
>> +     * For the case when _CCA is missing but platform requires it
>> +     * (i.e. is_coherent=0 && cca_seen=0), we do not call
>> +     * arch_setup_dma_ops() and fallback to arch-specific default
>> +     * handling.
>> +     */
>> +    if (adev->flags.cca_seen) {
>> +        if (!coherent && !IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
>> +            return;
>> +        arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
>
> how about using &adev->dev here, and just pass struct acpi_device *adev
> for this function?

Actually, I was using arch_setup_device_dma() in multiple places, and 
adev->dev is not necessary the same as *dev.  However, I am refactoring 
this function in V3. Anyways, thanks for reviewing.

Suravee

Suravee Suthikulpanit May 6, 2015, 10:16 p.m. UTC | #5

On 5/6/2015 5:21 PM, Rafael J. Wysocki wrote:
>>>> > >>+	bool
>>>> > >>+
>>>> > >>+config ACPI_SUPPORT_CCA_ZERO
>>> > >
>>> > >I guess this means "we support devices that can DMA, but are not coherent".
>>> > >right?
>> >
>> >Yes, basically when _CCA=0.
> So what about
>
> 	ARCH_SUPPORT_CACHE_INCOHERENT_DMA

Since this is specific to ACPI _CCA, I just want to be clear with the 
naming.

> or something similar?
>
>>>> > >>+	bool
>>>> > >>+
>>>> > >>   config ACPI_SLEEP
>>>> > >>   	bool
>>>> > >>   	depends on SUSPEND || HIBERNATION
>>>> > >>diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
>>>> > >>index 4bf7559..a6feca4 100644
>>>> > >>--- a/drivers/acpi/acpi_platform.c
>>>> > >>+++ b/drivers/acpi/acpi_platform.c
>>>> > >>@@ -108,9 +108,11 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
>>>> > >>   	if (IS_ERR(pdev))
>>>> > >>   		dev_err(&adev->dev, "platform device creation failed: %ld\n",
>>>> > >>   			PTR_ERR(pdev));
>>>> > >>-	else
>>>> > >>+	else {
>>> > >
>>> > >Please add braces to both branches when making such changes (as per CodingStyle).
>>> > >
>> >
>> >OK.
>> >
>>>> > >>+		acpi_setup_device_dma(adev, &pdev->dev);
>>> > >
>>> > >Why do we need to do that here (for the second time)?
>> >
>> >Because we are calling:
>> >    acpi_create_platform_device()
>> >      |--> platform_device_register_device_full()
>> >        |-->platform_device_alloc()
>> >
>> >This creates platform_device, which allocate a new platform_device->dev.
>> >This is not the same as the original acpi_device->dev that was created
>> >during acpi_add_single_object(). So, we have to set up the device
>> >coherency again.
> Ah, so the second arg is different now.
>
> Well, in that case, why do we need to set it up for the adev's dev member?
>

Just for sanity, since I don't know if adev->dev will be referenced 
anywhere else. This way, it's consistent for all copied of struct device 
generated.

Lemme know if you think that is unnecessary.

Thanks,

Suravee

Rafael J. Wysocki May 6, 2015, 10:21 p.m. UTC | #6

On Tuesday, May 05, 2015 11:15:37 PM Suravee Suthikulpanit wrote:
> [RESEND]
> 
> On 5/5/15 15:36, Rafael J. Wysocki wrote:
> > On Tuesday, May 05, 2015 10:12:05 AM Suravee Suthikulpanit wrote:
> >> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> >> index ab2cbb5..dd386e9 100644
> >> --- a/drivers/acpi/Kconfig
> >> +++ b/drivers/acpi/Kconfig
> >> @@ -54,6 +54,12 @@ config ACPI_GENERIC_GSI
> >>   config ACPI_SYSTEM_POWER_STATES_SUPPORT
> >>   	bool
> >>
> >> +config ACPI_MUST_HAVE_CCA
> >
> > ACPI_CCA_REQUIRED maybe?
> 
> Sure.
> 
> >
> >> +	bool
> >> +
> >> +config ACPI_SUPPORT_CCA_ZERO
> >
> > I guess this means "we support devices that can DMA, but are not coherent".
> > right?
> 
> Yes, basically when _CCA=0.

So what about

	ARCH_SUPPORT_CACHE_INCOHERENT_DMA

or something similar?

> >> +	bool
> >> +
> >>   config ACPI_SLEEP
> >>   	bool
> >>   	depends on SUSPEND || HIBERNATION
> >> diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
> >> index 4bf7559..a6feca4 100644
> >> --- a/drivers/acpi/acpi_platform.c
> >> +++ b/drivers/acpi/acpi_platform.c
> >> @@ -108,9 +108,11 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
> >>   	if (IS_ERR(pdev))
> >>   		dev_err(&adev->dev, "platform device creation failed: %ld\n",
> >>   			PTR_ERR(pdev));
> >> -	else
> >> +	else {
> >
> > Please add braces to both branches when making such changes (as per CodingStyle).
> >
> 
> OK.
> 
> >> +		acpi_setup_device_dma(adev, &pdev->dev);
> >
> > Why do we need to do that here (for the second time)?
> 
> Because we are calling:
>    acpi_create_platform_device()
>      |--> platform_device_register_device_full()
>        |-->platform_device_alloc()
> 
> This creates platform_device, which allocate a new platform_device->dev. 
> This is not the same as the original acpi_device->dev that was created 
> during acpi_add_single_object(). So, we have to set up the device 
> coherency again.

Ah, so the second arg is different now.

Well, in that case, why do we need to set it up for the adev's dev member?

> >> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> >> index 849b699..ac33b29 100644
> >> --- a/drivers/acpi/scan.c
> >> +++ b/drivers/acpi/scan.c
> >> @@ -11,6 +11,7 @@
> >>   #include <linux/kthread.h>
> >>   #include <linux/dmi.h>
> >>   #include <linux/nls.h>
> >> +#include <linux/dma-mapping.h>
> >>
> >>   #include <asm/pgtable.h>
> >>
> >> @@ -2137,6 +2138,66 @@ void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
> >>   	kfree(pnp->unique_id);
> >>   }
> >>
> >> +void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev)
> >> +{
> >> +	int coherent = acpi_dma_is_coherent(adev);
> >> +
> >> +	/**
> >> +	 * Currently, we only support DMA for devices that _CCA=1
> >> +	 * since this seems to be the case on most ACPI platforms.
> >> +	 *
> >> +	 * For the case when _CCA=0 (i.e. is_coherent=0 && cca_seen=1),
> >> +	 * we would rely on arch-specific cache maintenance for
> >> +	 * non-coherence DMA operations if architecture enables
> >> +	 * CONFIG_ACPI_SUPPORT_CCA_ZERO.
> >> +	 *
> >> +	 * For the case when _CCA is missing but platform requires it
> >> +	 * (i.e. is_coherent=0 && cca_seen=0), we do not call
> >> +	 * arch_setup_dma_ops() and fallback to arch-specific default
> >> +	 * handling.
> >> +	 */
> >> +	if (adev->flags.cca_seen) {
> >> +		if (!coherent && !IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
> >> +			return;
> >> +		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
> >
> > Oh dear.
> 
> I made a mistake here. This logic should also call arch_setup_dma_ops() 
> when cca_seen=0 and coherent=1 (e.g. when _CCA is not required and 
> default to coherent when it is missing). The current logic doesn't do that.
> 
> >
> > What about
> >
> > 	if (adev->flags.cca_seen && (coherent || IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO)))
> > 		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
> 
> What about:
> 	if (coherent ||
> 	    (adev->flags.cca_seen &&
> 			IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
> 		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);

Yes, that works.

> > I wonder how this is going to affect x86/ia64 too?
> >
> 
> This should not affect x86 since arch_setup_dma_ops() is currently not 
> implement for x86, and default to NOP (see include/linux/dma-mapping.h). 

OK

>   Also, on x86, _CCA is not required and default to 1 if missing.

Well, that's the point. :-)

Arnd Bergmann May 7, 2015, 9:07 a.m. UTC | #7

On Wednesday 06 May 2015 17:16:35 Suravee Suthikulanit wrote:
> On 5/6/2015 5:21 PM, Rafael J. Wysocki wrote:
> >>>> > >>+      bool
> >>>> > >>+
> >>>> > >>+config ACPI_SUPPORT_CCA_ZERO
> >>> > >
> >>> > >I guess this means "we support devices that can DMA, but are not coherent".
> >>> > >right?
> >> >
> >> >Yes, basically when _CCA=0.
> > So what about
> >
> >       ARCH_SUPPORT_CACHE_INCOHERENT_DMA
> 
> Since this is specific to ACPI _CCA, I just want to be clear with the 
> naming.

How about directly using the architecture names here, this is inherently
architecture specific, and it's more likely that if another architecture
gets added in the future that it will have other requirements.

	Arnd

Rafael J. Wysocki May 7, 2015, 8:18 p.m. UTC | #8

On Thursday, May 07, 2015 11:07:08 AM Arnd Bergmann wrote:
> On Wednesday 06 May 2015 17:16:35 Suravee Suthikulanit wrote:
> > On 5/6/2015 5:21 PM, Rafael J. Wysocki wrote:
> > >>>> > >>+      bool
> > >>>> > >>+
> > >>>> > >>+config ACPI_SUPPORT_CCA_ZERO
> > >>> > >
> > >>> > >I guess this means "we support devices that can DMA, but are not coherent".
> > >>> > >right?
> > >> >
> > >> >Yes, basically when _CCA=0.
> > > So what about
> > >
> > >       ARCH_SUPPORT_CACHE_INCOHERENT_DMA
> > 
> > Since this is specific to ACPI _CCA, I just want to be clear with the 
> > naming.
> 
> How about directly using the architecture names here, this is inherently
> architecture specific, and it's more likely that if another architecture
> gets added in the future that it will have other requirements.

Sounds reasonable to me.

Rafael

Patch

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index ab2cbb5..dd386e9 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -54,6 +54,12 @@  config ACPI_GENERIC_GSI
 config ACPI_SYSTEM_POWER_STATES_SUPPORT
 	bool
 
+config ACPI_MUST_HAVE_CCA
+	bool
+
+config ACPI_SUPPORT_CCA_ZERO
+	bool
+
 config ACPI_SLEEP
 	bool
 	depends on SUSPEND || HIBERNATION
diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c
index 4bf7559..a6feca4 100644
--- a/drivers/acpi/acpi_platform.c
+++ b/drivers/acpi/acpi_platform.c
@@ -108,9 +108,11 @@  struct platform_device *acpi_create_platform_device(struct acpi_device *adev)
 	if (IS_ERR(pdev))
 		dev_err(&adev->dev, "platform device creation failed: %ld\n",
 			PTR_ERR(pdev));
-	else
+	else {
+		acpi_setup_device_dma(adev, &pdev->dev);
 		dev_dbg(&adev->dev, "created platform device %s\n",
 			dev_name(&pdev->dev));
+	}
 
 	kfree(resources);
 	return pdev;
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 849b699..ac33b29 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -11,6 +11,7 @@ 
 #include <linux/kthread.h>
 #include <linux/dmi.h>
 #include <linux/nls.h>
+#include <linux/dma-mapping.h>
 
 #include <asm/pgtable.h>
 
@@ -2137,6 +2138,66 @@  void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
 	kfree(pnp->unique_id);
 }
 
+void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev)
+{
+	int coherent = acpi_dma_is_coherent(adev);
+
+	/**
+	 * Currently, we only support DMA for devices that _CCA=1
+	 * since this seems to be the case on most ACPI platforms.
+	 *
+	 * For the case when _CCA=0 (i.e. is_coherent=0 && cca_seen=1),
+	 * we would rely on arch-specific cache maintenance for
+	 * non-coherence DMA operations if architecture enables
+	 * CONFIG_ACPI_SUPPORT_CCA_ZERO.
+	 *
+	 * For the case when _CCA is missing but platform requires it
+	 * (i.e. is_coherent=0 && cca_seen=0), we do not call
+	 * arch_setup_dma_ops() and fallback to arch-specific default
+	 * handling.
+	 */
+	if (adev->flags.cca_seen) {
+		if (!coherent && !IS_ENABLED(CONFIG_ACPI_SUPPORT_CCA_ZERO))
+			return;
+		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
+	}
+}
+
+static void acpi_init_coherency(struct acpi_device *adev)
+{
+	unsigned long long cca = 0;
+	acpi_status status;
+	struct acpi_device *parent = adev->parent;
+
+	if (parent && parent->flags.cca_seen) {
+		/*
+		 * From ACPI spec, OSPM will ignore _CCA if an ancestor
+		 * already saw one.
+		 */
+		adev->flags.cca_seen = 1;
+		cca = acpi_dma_is_coherent(parent);
+	} else {
+		status = acpi_evaluate_integer(adev->handle, "_CCA",
+					       NULL, &cca);
+		if (ACPI_SUCCESS(status)) {
+			adev->flags.cca_seen = 1;
+		} else if (!IS_ENABLED(CONFIG_ACPI_MUST_HAVE_CCA)) {
+			/*
+			 * If architecture does not specify that _CCA is
+			 * required for DMA-able devices (e.g. x86),
+			 * we default to _CCA=1.
+			 */
+			cca = 1;
+		} else {
+			dev_err(&adev->dev, FW_BUG
+				"DMA is not setup due to missing _CCA.\n");
+		}
+	}
+
+	adev->flags.is_coherent = cca;
+	acpi_setup_device_dma(adev, &adev->dev);
+}
+
 void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 			     int type, unsigned long long sta)
 {
@@ -2155,6 +2216,7 @@  void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 	device->flags.visited = false;
 	device_initialize(&device->dev);
 	dev_set_uevent_suppress(&device->dev, true);
+	acpi_init_coherency(device);
 }
 
 void acpi_device_add_finalize(struct acpi_device *device)
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 8de4fa9..b804183 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -208,7 +208,9 @@  struct acpi_device_flags {
 	u32 visited:1;
 	u32 hotplug_notify:1;
 	u32 is_dock_station:1;
-	u32 reserved:23;
+	u32 is_coherent:1;
+	u32 cca_seen:1;
+	u32 reserved:21;
 };
 
 /* File System */
@@ -380,6 +382,13 @@  struct acpi_device {
 	void (*remove)(struct acpi_device *);
 };
 
+static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
+{
+	return adev && adev->flags.is_coherent;
+}
+
+void acpi_setup_device_dma(struct acpi_device *adev, struct device *dev);
+
 static inline bool is_acpi_node(struct fwnode_handle *fwnode)
 {
 	return fwnode && fwnode->type == FWNODE_ACPI;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index b10c4a6..d14e777 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -583,6 +583,11 @@  static inline int acpi_device_modalias(struct device *dev,
 	return -ENODEV;
 }
 
+static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
+{
+	return false;
+}
+
 #define ACPI_PTR(_ptr)	(NULL)
 
 #endif	/* !CONFIG_ACPI */