Subject: Re: [PATCH v3 0/5] ACPI: DMA ranges management
To: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        linux-acpi@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Will Deacon <will.deacon@arm.com>, Hanjun Guo <hanjun.guo@linaro.org>,
        Feng Kan <fkan@apm.com>, Jon Masters <jcm@redhat.com>,
        Robert Moore <robert.moore@intel.com>,
        Robin Murphy <robin.murphy@arm.com>, Zhang Rui <rui.zhang@intel.com>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Nate Watterson <nwatters@codeaurora.org>
References: <20170803123239.11359-1-lorenzo.pieralisi@arm.com>
From: Jeremy Linton <jeremy.linton@arm.com>
Message-ID: <61e15178-a6da-0459-34fc-83ff4ded8864@arm.com>
Date: Wed, 9 Aug 2017 16:14:43 -0500
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Hi,

Better late than never I guess..

On 08/03/2017 07:32 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(-)

Ok, despite being merged already I think its worthwhile to say that I've 
been testing this with:

Method(_DMA, 0, Serialized)
{
	Return (ResourceTemplate()
	{
		QWORDMemory(
		ResourceConsumer,
		PosDecode,          // _DEC
		MinFixed,           // _MIF
		MaxFixed,           // _MAF
		Prefetchable,       // _MEM
		ReadWrite,          // _RW
		0,                  // _GRA
		0x10000000,         // _MIN
		0x1fffffff,         // _MAX
		0x000000000,        // _TRA
		0x10000000,         // _LEN
		,
		,
		,
		)
	})
} // Method(_DMA)

(and a couple minor variations)

and a fair number of debug statements sprinkled around to verify that 
the IOVAs are appropriately limited. So I don't see anything wrong with 
the code and it appears to work and the devices behind a bridge limited 
like this continue to work as long as sane values are placed in the 
min/max/len fields.

Thanks,

Tested-by: Jeremy Linton <jeremy.linton@arm.com>