diff mbox

[V5,1/5] ACPI / scan: Parse _CCA and setup device coherency

Message ID 1432159758-4486-2-git-send-email-Suravee.Suthikulpanit@amd.com (mailing list archive)
State Not Applicable
Delegated to: Herbert Xu
Headers show

Commit Message

Suravee Suthikulpanit May 20, 2015, 10:09 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 <msalter@redhat.com>
Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
---
 drivers/acpi/Kconfig         |  3 +++
 drivers/acpi/acpi_platform.c |  2 +-
 drivers/acpi/glue.c          |  5 +++++
 drivers/acpi/scan.c          | 35 +++++++++++++++++++++++++++++++++++
 include/acpi/acpi_bus.h      | 37 ++++++++++++++++++++++++++++++++++++-
 include/linux/acpi.h         |  5 +++++
 6 files changed, 85 insertions(+), 2 deletions(-)

Comments

Rafael J. Wysocki May 22, 2015, 9:56 p.m. UTC | #1
On Wednesday, May 20, 2015 05:09:14 PM 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 <msalter@redhat.com>
> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
> ---
>  drivers/acpi/Kconfig         |  3 +++
>  drivers/acpi/acpi_platform.c |  2 +-
>  drivers/acpi/glue.c          |  5 +++++
>  drivers/acpi/scan.c          | 35 +++++++++++++++++++++++++++++++++++
>  include/acpi/acpi_bus.h      | 37 ++++++++++++++++++++++++++++++++++++-
>  include/linux/acpi.h         |  5 +++++
>  6 files changed, 85 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index ab2cbb5..212735f 100644
> --- a/drivers/acpi/Kconfig
> +++ b/drivers/acpi/Kconfig
> @@ -54,6 +54,9 @@ config ACPI_GENERIC_GSI
>  config ACPI_SYSTEM_POWER_STATES_SUPPORT
>  	bool
>  
> +config ACPI_CCA_REQUIRED
> +	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..06a67d5 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 = DMA_BIT_MASK(32);
> +	pdevinfo.dma_mask = acpi_check_dma(adev, NULL) ? 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 39c485b..b9657af 100644
> --- a/drivers/acpi/glue.c
> +++ b/drivers/acpi/glue.c
> @@ -13,6 +13,7 @@
>  #include <linux/slab.h>
>  #include <linux/rwsem.h>
>  #include <linux/acpi.h>
> +#include <linux/dma-mapping.h>
>  
>  #include "internal.h"
>  
> @@ -167,6 +168,7 @@ 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) {
> @@ -223,6 +225,9 @@ 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);
> +

Well, so is this going to work for PCI too after all?

>  	acpi_physnode_link_name(physical_node_name, node_id);
>  	retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
>  				   physical_node_name);
Suravee Suthikulpanit May 22, 2015, 10:24 p.m. UTC | #2
Not sure if this went out earlier. So I am resending.

On 5/22/15 16:56, Rafael J. Wysocki wrote:
>> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
>> >index 39c485b..b9657af 100644
>> >--- a/drivers/acpi/glue.c
>> >+++ b/drivers/acpi/glue.c
>> >@@ -13,6 +13,7 @@
>> >  #include <linux/slab.h>
>> >  #include <linux/rwsem.h>
>> >  #include <linux/acpi.h>
>> >+#include <linux/dma-mapping.h>
>> >
>> >  #include "internal.h"
>> >
>> >@@ -167,6 +168,7 @@ 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) {
>> >@@ -223,6 +225,9 @@ 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);
>> >+
> Well, so is this going to work for PCI too after all?
>

No, as Bjorn suggested, PCI changes for setting DMA coherent from _CCA 
(patch 3/6 in V4) will be submitted separately. We are working on 
cleaning up and up-streaming the PCI ACPI support for ARM64.

Thanks,

Suravee

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Rafael J. Wysocki May 22, 2015, 11:05 p.m. UTC | #3
On Friday, May 22, 2015 05:24:15 PM Suravee Suthikulanit wrote:
> Not sure if this went out earlier. So I am resending.
> 
> On 5/22/15 16:56, Rafael J. Wysocki wrote:
> >> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> >> >index 39c485b..b9657af 100644
> >> >--- a/drivers/acpi/glue.c
> >> >+++ b/drivers/acpi/glue.c
> >> >@@ -13,6 +13,7 @@
> >> >  #include <linux/slab.h>
> >> >  #include <linux/rwsem.h>
> >> >  #include <linux/acpi.h>
> >> >+#include <linux/dma-mapping.h>
> >> >
> >> >  #include "internal.h"
> >> >
> >> >@@ -167,6 +168,7 @@ 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) {
> >> >@@ -223,6 +225,9 @@ 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);
> >> >+
> > Well, so is this going to work for PCI too after all?
> >
> 
> No, as Bjorn suggested, PCI changes for setting DMA coherent from _CCA 
> (patch 3/6 in V4) will be submitted separately. We are working on 
> cleaning up and up-streaming the PCI ACPI support for ARM64.

OK, but acpi_bind_one() is called for PCI devices too.  Won't that be a problem?
Suravee Suthikulpanit May 23, 2015, 12:15 a.m. UTC | #4
On 5/22/2015 6:05 PM, Rafael J. Wysocki wrote:
> On Friday, May 22, 2015 05:24:15 PM Suravee Suthikulanit wrote:
>> Not sure if this went out earlier. So I am resending.
>>
>> On 5/22/15 16:56, Rafael J. Wysocki wrote:
>>>> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
>>>>> index 39c485b..b9657af 100644
>>>>> --- a/drivers/acpi/glue.c
>>>>> +++ b/drivers/acpi/glue.c
>>>>> @@ -13,6 +13,7 @@
>>>>>   #include <linux/slab.h>
>>>>>   #include <linux/rwsem.h>
>>>>>   #include <linux/acpi.h>
>>>>> +#include <linux/dma-mapping.h>
>>>>>
>>>>>   #include "internal.h"
>>>>>
>>>>> @@ -167,6 +168,7 @@ 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) {
>>>>> @@ -223,6 +225,9 @@ 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);
>>>>> +
>>> Well, so is this going to work for PCI too after all?
>>>
>>
>> No, as Bjorn suggested, PCI changes for setting DMA coherent from _CCA
>> (patch 3/6 in V4) will be submitted separately. We are working on
>> cleaning up and up-streaming the PCI ACPI support for ARM64.
>
> OK, but acpi_bind_one() is called for PCI devices too.  Won't that be a problem?
>
>
 >
In this case, we would be going through the following call path:

   --> pci_device_add()
    |--> pci_dma_configure() ** 1 **
    |--> device_add()
      |--> platform_notify()
        |--> acpi_platform_notify()
         |--> acpi_bind_one() ** 2 **

At (1), we would be calling arch_setup_dma_ops() with the PCI host 
bridge _CCA information. So, it should have already taken care of 
setting up device coherency here.

At (2), if there is no acpi_dev for endpoint devices (which I believe 
this is normally the case), it would return early and skip 
arch_setup_dma_ops().

At (2), if there is an acpi_dev, the coherent_dma flag should have 
already been setup by the acpi_init_device_object during ACPI scan. 
However, I am not certain about this case since I don't have the DSDT 
containing  PCI endpoint devices to test with.

Thanks,

Suravee

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Rafael J. Wysocki May 23, 2015, 1:25 a.m. UTC | #5
On Friday, May 22, 2015 07:15:17 PM Suravee Suthikulanit wrote:
> On 5/22/2015 6:05 PM, Rafael J. Wysocki wrote:
> > On Friday, May 22, 2015 05:24:15 PM Suravee Suthikulanit wrote:
> >> Not sure if this went out earlier. So I am resending.
> >>
> >> On 5/22/15 16:56, Rafael J. Wysocki wrote:
> >>>> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> >>>>> index 39c485b..b9657af 100644
> >>>>> --- a/drivers/acpi/glue.c
> >>>>> +++ b/drivers/acpi/glue.c
> >>>>> @@ -13,6 +13,7 @@
> >>>>>   #include <linux/slab.h>
> >>>>>   #include <linux/rwsem.h>
> >>>>>   #include <linux/acpi.h>
> >>>>> +#include <linux/dma-mapping.h>
> >>>>>
> >>>>>   #include "internal.h"
> >>>>>
> >>>>> @@ -167,6 +168,7 @@ 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) {
> >>>>> @@ -223,6 +225,9 @@ 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);
> >>>>> +
> >>> Well, so is this going to work for PCI too after all?
> >>>
> >>
> >> No, as Bjorn suggested, PCI changes for setting DMA coherent from _CCA
> >> (patch 3/6 in V4) will be submitted separately. We are working on
> >> cleaning up and up-streaming the PCI ACPI support for ARM64.
> >
> > OK, but acpi_bind_one() is called for PCI devices too.  Won't that be a problem?
> >
> >
>  >
> In this case, we would be going through the following call path:
> 
>    --> pci_device_add()
>     |--> pci_dma_configure() ** 1 **
>     |--> device_add()
>       |--> platform_notify()
>         |--> acpi_platform_notify()
>          |--> acpi_bind_one() ** 2 **
> 
> At (1), we would be calling arch_setup_dma_ops() with the PCI host 
> bridge _CCA information. So, it should have already taken care of 
> setting up device coherency here.
> 
> At (2), if there is no acpi_dev for endpoint devices (which I believe 
> this is normally the case), it would return early and skip 
> arch_setup_dma_ops().

That's not correct.  There may be ACPI companions for endpoint devices too.


> At (2), if there is an acpi_dev, the coherent_dma flag should have 
> already been setup by the acpi_init_device_object during ACPI scan.

That one sets the flag for the *ACPI* *companion* of the device, which
I'm still thinking is pointless, isn't it?


> However, I am not certain about this case since I don't have the DSDT 
> containing  PCI endpoint devices to test with.

Every x86 PC has them (as far as I can say), but in that case there's no
_CCA and they are all coherent.
Suravee Suthikulpanit May 23, 2015, 1:38 a.m. UTC | #6
On 5/22/2015 8:25 PM, Rafael J. Wysocki wrote:
> On Friday, May 22, 2015 07:15:17 PM Suravee Suthikulanit wrote:
>> On 5/22/2015 6:05 PM, Rafael J. Wysocki wrote:
>>> On Friday, May 22, 2015 05:24:15 PM Suravee Suthikulanit wrote:
>>>> Not sure if this went out earlier. So I am resending.
>>>>
>>>> On 5/22/15 16:56, Rafael J. Wysocki wrote:
>>>>>> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
>>>>>>> index 39c485b..b9657af 100644
>>>>>>> --- a/drivers/acpi/glue.c
>>>>>>> +++ b/drivers/acpi/glue.c
>>>>>>> @@ -13,6 +13,7 @@
>>>>>>>    #include <linux/slab.h>
>>>>>>>    #include <linux/rwsem.h>
>>>>>>>    #include <linux/acpi.h>
>>>>>>> +#include <linux/dma-mapping.h>
>>>>>>>
>>>>>>>    #include "internal.h"
>>>>>>>
>>>>>>> @@ -167,6 +168,7 @@ 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) {
>>>>>>> @@ -223,6 +225,9 @@ 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);
>>>>>>> +
>>>>> Well, so is this going to work for PCI too after all?
>>>>>
>>>>
>>>> No, as Bjorn suggested, PCI changes for setting DMA coherent from _CCA
>>>> (patch 3/6 in V4) will be submitted separately. We are working on
>>>> cleaning up and up-streaming the PCI ACPI support for ARM64.
>>>
>>> OK, but acpi_bind_one() is called for PCI devices too.  Won't that be a problem?
>>>
>>>
>>   >
>> In this case, we would be going through the following call path:
>>
>>     --> pci_device_add()
>>      |--> pci_dma_configure() ** 1 **
>>      |--> device_add()
>>        |--> platform_notify()
>>          |--> acpi_platform_notify()
>>           |--> acpi_bind_one() ** 2 **
>>
>> At (1), we would be calling arch_setup_dma_ops() with the PCI host
>> bridge _CCA information. So, it should have already taken care of
>> setting up device coherency here.
>>
>> At (2), if there is no acpi_dev for endpoint devices (which I believe
>> this is normally the case), it would return early and skip
>> arch_setup_dma_ops().
>
> That's not correct.  There may be ACPI companions for endpoint devices too.

Ok. Duly noted :)

>> At (2), if there is an acpi_dev, the coherent_dma flag should have
>> already been setup by the acpi_init_device_object during ACPI scan.
>
> That one sets the flag for the *ACPI* *companion* of the device, which
> I'm still thinking is pointless, isn't it?

When you say pointless, are you referring to the part where we are end 
up calling arch_setup_dma_coherent() twice in this case? I am not quite 
following your point.

>> However, I am not certain about this case since I don't have the DSDT
>> containing  PCI endpoint devices to test with.
>
> Every x86 PC has them (as far as I can say), but in that case there's no
> _CCA and they are all coherent.

Ok.

Thanks,
Suravee


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diff mbox

Patch

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index ab2cbb5..212735f 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -54,6 +54,9 @@  config ACPI_GENERIC_GSI
 config ACPI_SYSTEM_POWER_STATES_SUPPORT
 	bool
 
+config ACPI_CCA_REQUIRED
+	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..06a67d5 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 = DMA_BIT_MASK(32);
+	pdevinfo.dma_mask = acpi_check_dma(adev, NULL) ? 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 39c485b..b9657af 100644
--- a/drivers/acpi/glue.c
+++ b/drivers/acpi/glue.c
@@ -13,6 +13,7 @@ 
 #include <linux/slab.h>
 #include <linux/rwsem.h>
 #include <linux/acpi.h>
+#include <linux/dma-mapping.h>
 
 #include "internal.h"
 
@@ -167,6 +168,7 @@  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) {
@@ -223,6 +225,9 @@  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);
+
 	acpi_physnode_link_name(physical_node_name, node_id);
 	retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
 				   physical_node_name);
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 849b699..fdedb63 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 +2138,39 @@  void acpi_free_pnp_ids(struct acpi_device_pnp *pnp)
 	kfree(pnp->unique_id);
 }
 
+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 = parent->flags.coherent_dma;
+	} 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_CCA_REQUIRED))
+			/*
+			 * If architecture does not specify that _CCA is
+			 * required for DMA-able devices (e.g. x86),
+			 * we default to _CCA=1.
+			 */
+			cca = 1;
+		else
+			acpi_handle_debug(adev->handle,
+					  "ACPI device is missing _CCA.\n");
+	}
+
+	adev->flags.coherent_dma = cca;
+}
+
 void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
 			     int type, unsigned long long sta)
 {
@@ -2155,6 +2189,7 @@  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..cbd1b57 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 coherent_dma:1;
+	u32 cca_seen:1;
+	u32 reserved:21;
 };
 
 /* File System */
@@ -380,6 +382,39 @@  struct acpi_device {
 	void (*remove)(struct acpi_device *);
 };
 
+static inline bool acpi_check_dma(struct acpi_device *adev, bool *coherent)
+{
+	bool ret = false;
+
+	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)
+			*coherent = adev->flags.coherent_dma;
+	}
+	return ret;
+}
+
 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..30c81ac 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_check_dma(struct acpi_device *adev, bool *coherent)
+{
+	return false;
+}
+
 #define ACPI_PTR(_ptr)	(NULL)
 
 #endif	/* !CONFIG_ACPI */