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

[Suravee Suthikulpanit]

On 5/5/15 22:13, Hanjun Guo wrote:
> On 2015å05æ05æ 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@xxxxxxxxxx>
> > Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> > ---
> > 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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