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SubjectRe: [V3 PATCH 1/5] ACPI / scan: Parse _CCA and setup device coherency
Date
On Thursday, May 07, 2015 07:37:12 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 | 6 ++++++
> drivers/acpi/acpi_platform.c | 10 +++++++---
> drivers/acpi/scan.c | 42 ++++++++++++++++++++++++++++++++++++++++++
> include/acpi/acpi_bus.h | 32 +++++++++++++++++++++++++++++++-
> include/linux/acpi.h | 10 ++++++++++
> 5 files changed, 96 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
> index ab2cbb5..7822149 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_CCA_REQUIRED
> + bool
> +
> +config ARM64_SUPPORT_ACPI_CCA_ZERO

Hmm. I guess the Arnd's idea what to simply use CONFIG_ARM64 directly instead
of adding this new option.

> + 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..a084ea0 100644
> --- a/drivers/acpi/acpi_platform.c
> +++ b/drivers/acpi/acpi_platform.c
> @@ -103,14 +103,18 @@ 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_dma_is_supported(adev)? DMA_BIT_MASK(32): 0;

Spaces before the "?" and ":", please.

> pdev = platform_device_register_full(&pdevinfo);
> - if (IS_ERR(pdev))
> + if (IS_ERR(pdev)) {
> dev_err(&adev->dev, "platform device creation failed: %ld\n",
> PTR_ERR(pdev));
> - else
> + } else {
> + if (acpi_dma_is_supported(adev))
> + arch_setup_dma_ops(&pdev->dev, 0, 0, NULL,
> + acpi_dma_is_coherent(adev));

OK, so I understand why this is needed, but ->

> 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..0976dc2 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 +2138,46 @@ 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;
> + struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +
> + 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_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_get_name(adev->handle, ACPI_FULL_PATHNAME, &buffer);
> + pr_debug("ACPI device %s is missing _CCA.\n",
> + (char *) buffer.pointer);
> + kfree(buffer.pointer);
> + }
> + }
> +
> + adev->flags.is_coherent = cca;
> + if (acpi_dma_is_supported(adev))
> + arch_setup_dma_ops(&adev->dev, 0, 0, NULL,
> + acpi_dma_is_coherent(adev));

Why do we need this one? adev->dev is not a device, it is an ACPI namespace
node representation. Why do you want to set up DMA ops for it?

Would you set up DMA ops for a struct device_node?

> +}
> +
> void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
> int type, unsigned long long sta)
> {
> @@ -2155,6 +2196,7 @@ 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..17fb630 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 +382,34 @@ struct acpi_device {
> void (*remove)(struct acpi_device *);
> };
>
> +static inline bool acpi_dma_is_supported(struct acpi_device *adev)
> +{
> + /**
> + * Currently, we mainly support _CCA=1 (i.e. is_coherent=1)
> + * This should be equivalent to specifyig dma-coherent for
> + * a device in OF.
> + *
> + * 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 specifies
> + * _XXX_SUPPORT_CCA_ZERO. Otherwise, we do not support
> + * DMA on this device and fallback to arch-specific default
> + * handling.
> + *
> + * For the case when _CCA is missing (i.e. cca_seen=0) but
> + * platform specifies ACPI_CCA_REQUIRED, we do not support DMA,
> + * and fallback to arch-specific default handling.
> + */
> + return adev && (adev->flags.is_coherent ||
> + (adev->flags.cca_seen &&
> + IS_ENABLED(CONFIG_ARM64_SUPPORT_ACPI_CCA_ZERO)));

So what exactly would be wrong with using IS_ENABLED(CONFIG_ARM64) here?

> +}
> +
> +static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
> +{
> + return adev && adev->flags.is_coherent;
> +}
> +
> 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..baccf3b 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -583,6 +583,16 @@ static inline int acpi_device_modalias(struct device *dev,
> return -ENODEV;
> }
>
> +static inline bool acpi_dma_is_supported(struct acpi_device *adev)
> +{
> + return false;
> +}
> +
> +static inline bool acpi_dma_is_coherent(struct acpi_device *adev)
> +{
> + return false;
> +}
> +
> #define ACPI_PTR(_ptr) (NULL)
>
> #endif /* !CONFIG_ACPI */
>

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.


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