netdev - Re: [V2 PATCH 1/5] ACPI / scan: Parse

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Message-ID: <554995EC.3030601@amd.com>
Date:	Tue, 5 May 2015 23:17:48 -0500
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>, <rjw@...ysocki.net>,
	<lenb@...nel.org>, <catalin.marinas@....com>,
	<will.deacon@....com>, <thomas.lendacky@....com>,
	<herbert@...dor.apana.org.au>, <davem@...emloft.net>
CC:	<msalter@...hat.com>, <al.stone@...aro.org>,
	<grant.likely@...aro.org>, <arnd@...db.de>, <leo.duran@....com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linaro-acpi@...ts.linaro.org>, <netdev@...r.kernel.org>,
	<linux-crypto@...r.kernel.org>
Subject: Re: [V2 PATCH 1/5] ACPI / scan: Parse _CCA and setup device coherency

On 5/5/15 22:13, Hanjun Guo wrote:
> On 2015年05月05日 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 <msalter@...hat.com>
>> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>> ---
>> 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
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