Re: [PATCH v3 0/5] ACPI: DMA ranges management

[Nate Watterson <nwatters@codeaurora.org>]

Hi Lorenzo,

On 8/3/2017 8:32 AM, Lorenzo Pieralisi wrote:
> This patch series is v3 of a previous posting:
> 
> v2->v3:
> 	- Fixed DMA masks computation
>          - Fixed size computation overflow in acpi_dma_get_range()
> 
> v1->v2:
> 	- Reworked acpi_dma_get_range() flow and logs
> 	- Added IORT named component address limits
> 	- Renamed acpi_dev_get_resources() helper function
> 	- Rebased against v4.13-rc3
> 
> v2: http://lkml.kernel.org/r/20170731152323.32488-1-lorenzo.pieralisi@arm.com
> v1: http://lkml.kernel.org/r/20170720144517.32529-1-lorenzo.pieralisi@arm.com
> 
> -- Original cover letter --
> 
> As reported in:
> 
> http://lkml.kernel.org/r/CAL85gmA_SSCwM80TKdkZqEe+S1beWzDEvdki1kpkmUTDRmSP7g@mail.gmail.com
> 
> the bus connecting devices to an IOMMU bus can be smaller in size than
> the IOMMU input address bits which results in devices DMA HW bugs in
> particular related to IOVA allocation (ie chopping of higher address
> bits owing to system bus HW capabilities mismatch with the IOMMU).
> 
> Fortunately this problem can be solved through an already present but never
> used ACPI 6.2 firmware bindings (ie _DMA object) allowing to define the DMA
> window for a specific bus in ACPI and therefore all upstream devices
> connected to it.
> 
> This small patch series enables _DMA parsing in ACPI core code and
> use it in ACPI IORT code in order to detect DMA ranges for devices and
> update their data structures to make them work with their related DMA
> addressing restrictions.
> 
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Hanjun Guo <hanjun.guo@linaro.org>
> Cc: Feng Kan <fkan@apm.com>
> Cc: Jon Masters <jcm@redhat.com>
> Cc: Robert Moore <robert.moore@intel.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Zhang Rui <rui.zhang@intel.com>
> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
> 
> Lorenzo Pieralisi (5):
>    ACPICA: resource_mgr: Allow _DMA method in walk resources
>    ACPI: Make acpi_dev_get_resources() method agnostic
>    ACPI: Introduce DMA ranges parsing
>    ACPI: Make acpi_dma_configure() DMA regions aware
>    ACPI/IORT: Add IORT named component memory address limits
> 
>   drivers/acpi/acpica/rsxface.c |  7 ++--
>   drivers/acpi/arm64/iort.c     | 57 ++++++++++++++++++++++++++-
>   drivers/acpi/resource.c       | 82 +++++++++++++++++++++++++++++---------
>   drivers/acpi/scan.c           | 91 +++++++++++++++++++++++++++++++++++++++----
>   include/acpi/acnames.h        |  1 +
>   include/acpi/acpi_bus.h       |  2 +
>   include/linux/acpi.h          |  8 ++++
>   include/linux/acpi_iort.h     |  5 ++-
>   8 files changed, 219 insertions(+), 34 deletions(-)
> 

I tested with named components and with _DMA objects at a variety of
sizes and verified the configured masks matched the expected values.

Tested-by: Nate Watterson <nwatters@codeaurora.org>

One general question I had while testing the patch is whether it is
possible to define a complete 64-bit range using the _DMA method. For
instance, to get a 64-bit dma_mask I had to use a non-zero MIN value
so that LEN would not overflow.

QWORDMemory(
	ResourceConsumer,
	PosDecode,       // _DEC
	MinFixed,        // _MIF
	MaxFixed,        // _MAF
	Prefetchable,    // _MEM
	ReadWrite,       // _RW
	0,               // _GRA
	0x1000,               // _MIN
	0xffffffffffffffff,   // _MAX
	0x0,                  // _TRA
	0xfffffffffffff000,   // _LEN
	,
	,
	,
)

-Nate

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