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    SubjectRe: [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@redhat.com>
    >> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.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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