Re: [PATCH v5 06/14] drivers: acpi: implement acpi_dma_configure

[Robin Murphy <robin.murphy@arm.com>]

On 09/09/16 15:23, Lorenzo Pieralisi wrote:
> On DT based systems, the of_dma_configure() API implements DMA
> configuration for a given device. On ACPI systems an API equivalent to
> of_dma_configure() is missing which implies that it is currently not
> possible to set-up DMA operations for devices through the ACPI generic
> kernel layer.
> 
> This patch fills the gap by introducing acpi_dma_configure/deconfigure()
> calls that for now are just wrappers around arch_setup_dma_ops() and
> arch_teardown_dma_ops() and also updates ACPI and PCI core code to use
> the newly introduced acpi_dma_configure/acpi_dma_deconfigure functions.
> 
> The DMA range size passed to arch_setup_dma_ops() is sized according
> to the device coherent_dma_mask (starting at address 0x0), mirroring the
> DT probing path behaviour when a dma-ranges property is not provided
> for the device being probed; this changes the current arch_setup_dma_ops()
> call parameters in the ACPI probing case, but since arch_setup_dma_ops()
> is a NOP on all architectures but ARM/ARM64 this patch does not change
> the current kernel behaviour on them.
> 
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Acked-by: Bjorn Helgaas <bhelgaas@google.com> [pci]
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Tomasz Nowicki <tn@semihalf.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> ---
>  drivers/acpi/glue.c     |  4 ++--
>  drivers/acpi/scan.c     | 24 ++++++++++++++++++++++++
>  drivers/pci/probe.c     |  3 +--
>  include/acpi/acpi_bus.h |  2 ++
>  include/linux/acpi.h    |  5 +++++
>  5 files changed, 34 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
> index 5ea5dc2..f8d6564 100644
> --- a/drivers/acpi/glue.c
> +++ b/drivers/acpi/glue.c
> @@ -227,8 +227,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
>  
>  	attr = acpi_get_dma_attr(acpi_dev);
>  	if (attr != DEV_DMA_NOT_SUPPORTED)
> -		arch_setup_dma_ops(dev, 0, 0, NULL,
> -				   attr == DEV_DMA_COHERENT);
> +		acpi_dma_configure(dev, attr);
>  
>  	acpi_physnode_link_name(physical_node_name, node_id);
>  	retval = sysfs_create_link(&acpi_dev->dev.kobj, &dev->kobj,
> @@ -251,6 +250,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
>  	return 0;
>  
>   err:
> +	acpi_dma_deconfigure(dev);
>  	ACPI_COMPANION_SET(dev, NULL);
>  	put_device(dev);
>  	put_device(&acpi_dev->dev);
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index e878fc7..9614232 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1370,6 +1370,30 @@ enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
>  		return DEV_DMA_NON_COHERENT;
>  }
>  
> +/**
> + * acpi_dma_configure - Set-up DMA configuration for the device.
> + * @dev: The pointer to the device
> + * @attr: device dma attributes
> + */
> +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr)
> +{
> +	/*
> +	 * Assume dma valid range starts at 0 and covers the whole
> +	 * coherent_dma_mask.
> +	 */
> +	arch_setup_dma_ops(dev, 0, dev->coherent_dma_mask + 1, NULL,
> +			   attr == DEV_DMA_COHERENT);

This looks a bit hairy - if we're setting up the DMA configuration at
this point can we really always rely on the device already having a
valid DMA mask? I think it would make sense to at least check, and apply
the standard default 32-bit mask  if not.

> +}
> +
> +/**
> + * acpi_dma_deconfigure - Tear-down DMA configuration for the device.
> + * @dev: The pointer to the device
> + */
> +void acpi_dma_deconfigure(struct device *dev)
> +{
> +	arch_teardown_dma_ops(dev);
> +}

As touched upon in the dwc-usb3 thread, is it worth exporting these for
the benefit of modular bus/glue code, to match of_dma_configure()?

> +
>  static void acpi_init_coherency(struct acpi_device *adev)
>  {
>  	unsigned long long cca = 0;
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 93f280d..e96d482 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -1734,8 +1734,7 @@ static void pci_dma_configure(struct pci_dev *dev)
>  		if (attr == DEV_DMA_NOT_SUPPORTED)
>  			dev_warn(&dev->dev, "DMA not supported.\n");
>  		else
> -			arch_setup_dma_ops(&dev->dev, 0, 0, NULL,
> -					   attr == DEV_DMA_COHERENT);
> +			acpi_dma_configure(&dev->dev, attr);
>  	}

What about non-PCI stuff? I see there's at least an
acpi_create_platform_device() which I'd also kind of expect to see as a
caller (which indeed might also tie in with the aforementioned default
mask initialisation).

Robin.

>  
>  	pci_put_host_bridge_device(bridge);
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index c1a524d..4242c31 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -573,6 +573,8 @@ struct acpi_pci_root {
>  
>  bool acpi_dma_supported(struct acpi_device *adev);
>  enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev);
> +void acpi_dma_configure(struct device *dev, enum dev_dma_attr attr);
> +void acpi_dma_deconfigure(struct device *dev);
>  
>  struct acpi_device *acpi_find_child_device(struct acpi_device *parent,
>  					   u64 address, bool check_children);
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index c5eaf2f..05d4e48 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -729,6 +729,11 @@ static inline enum dev_dma_attr acpi_get_dma_attr(struct acpi_device *adev)
>  	return DEV_DMA_NOT_SUPPORTED;
>  }
>  
> +static inline void acpi_dma_configure(struct device *dev,
> +				      enum dev_dma_attr attr) { }
> +
> +static inline void acpi_dma_deconfigure(struct device *dev) { }
> +
>  #define ACPI_PTR(_ptr)	(NULL)
>  
>  static inline void acpi_device_set_enumerated(struct acpi_device *adev)
>