Re: [PATCH edk2-platforms 1/1] Platform/RaspberryPi/AcpiTables: add a IORT ACPI table to limit XHCI DMA

["Ard Biesheuvel" <ard.biesheuvel@arm.com>]

On 10/11/20 7:25 PM, Andrei Warkentin wrote:
> Hi Ard,
> 
> This makes sense to me. Glad there's a way forward to support such 
> systems with ACPI in Linux.
> 
> Could the other "legacy" devices behind the GPU be handled similarly? I 
> mean the ones with the 1GB DMA limit. Not this change, of course.
> 

Yes. Anything we describe in the namespace can be added here as a named 
component, with the associated address limit.

> Reviewed-by: Andrei Warkentin <awarkentin@vmware.com>
> 

Thanks,

> ------------------------------------------------------------------------
> *From:* Ard Biesheuvel <ard.biesheuvel@arm.com>
> *Sent:* Sunday, October 11, 2020 3:20 AM
> *To:* devel@edk2.groups.io <devel@edk2.groups.io>
> *Cc:* Ard Biesheuvel <ard.biesheuvel@arm.com>; Samer El-Haj-Mahmoud 
> <Samer.El-Haj-Mahmoud@arm.com>; Jeremy Linton <jeremy.linton@arm.com>; 
> Pete Batard <pete@akeo.ie>; Andrei Warkentin <awarkentin@vmware.com>; 
> Leif Lindholm <leif@nuviainc.com>
> *Subject:* [PATCH edk2-platforms 1/1] Platform/RaspberryPi/AcpiTables: 
> add a IORT ACPI table to limit XHCI DMA
> Add an IORT table that will limit XHCI DMA to 2 GB, by setting the
> DMA width to 31 bits. This is needed for Linux/arm64, which can
> only reliably deal with devices that are unable to perform DMA to
> the entire 32-bit address range if it can discover their existence
> early during boot, and this is before the ACPI interpreter is up
> and running (which rules out calling the _DMA method of the XHC0
> object)
> 
> Cc: Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@arm.com>
> Cc: Jeremy Linton <jeremy.linton@arm.com>
> Cc: Pete Batard <pete@akeo.ie>
> Cc: Andrei Warkentin <awarkentin@vmware.com>
> Cc: Leif Lindholm <leif@nuviainc.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
> ---
> Related discussions here:
> 
> https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flinux-arm-kernel%2F20201001161740.29064-1-nsaenzjulienne%40suse.de%2F&amp;data=04%7C01%7Cawarkentin%40vmware.com%7C0ceb573430144cf5a9c308d86dbe9d15%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C1%7C637380012741008284%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=Z1MavubU27xkVXFXSSLtobrwpKSmerA9y9uRZNDd2Nw%3D&amp;reserved=0
> https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flinux-acpi%2F20201010093153.30177-1-ardb%40kernel.org%2F&amp;data=04%7C01%7Cawarkentin%40vmware.com%7C0ceb573430144cf5a9c308d86dbe9d15%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C1%7C637380012741008284%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=JrfduAeqAJqiFzP8CrwnTigwy21SIJYviMW6IkdA8KI%3D&amp;reserved=0
> 
> On Linux, a _DMA method supersedes the IORT, and so the 3 GB limit will
> be used at runtime. IOW, streaming DMA will be permitted to the entire
> 3 GB region, but if shared buffers or bounce buffers are needed, they
> will be allocated from the first 2 GB of DRAM.
> 
> We may need to offer some guidance on this in the IORT spec, i.e., which
> value takes precedence if the IORT and the _DMA method disagree.
> 
>   Platform/RaspberryPi/AcpiTables/AcpiTables.inf |  1 +
>   Platform/RaspberryPi/AcpiTables/Iort.aslc      | 58 ++++++++++++++++++++
>   2 files changed, 59 insertions(+)
> 
> diff --git a/Platform/RaspberryPi/AcpiTables/AcpiTables.inf 
> b/Platform/RaspberryPi/AcpiTables/AcpiTables.inf
> index c40c32e16ff7..d2cce074e56c 100644
> --- a/Platform/RaspberryPi/AcpiTables/AcpiTables.inf
> +++ b/Platform/RaspberryPi/AcpiTables/AcpiTables.inf
> @@ -29,6 +29,7 @@ [Sources]
>     Fadt.aslc
>     Dbg2.aslc
>     Gtdt.aslc
> +  Iort.aslc
>     Dsdt.asl
>     Csrt.aslc
>     Spcr.aslc
> diff --git a/Platform/RaspberryPi/AcpiTables/Iort.aslc 
> b/Platform/RaspberryPi/AcpiTables/Iort.aslc
> new file mode 100644
> index 000000000000..1351e8f7b262
> --- /dev/null
> +++ b/Platform/RaspberryPi/AcpiTables/Iort.aslc
> @@ -0,0 +1,58 @@
> +/** @file
> +
> +  Copyright (c) 2020, Arm, Ltd. All rights reserved.<BR>
> +
> +  SPDX-License-Identifier: BSD-2-Clause-Patent
> +
> +**/
> +
> +#include <IndustryStandard/IoRemappingTable.h>
> +
> +#include "AcpiTables.h"
> +
> +#pragma pack(1)
> +
> +typedef struct {
> +  EFI_ACPI_6_0_IO_REMAPPING_NAMED_COMP_NODE Node;
> +  CONST CHAR8                               Name[16];
> +} RPI4_NC_NODE;
> +
> +typedef struct {
> +  EFI_ACPI_6_0_IO_REMAPPING_TABLE      Iort;
> +  RPI4_NC_NODE                         NamedCompNode;
> +} RPI4_IO_REMAPPING_STRUCTURE;
> +
> +STATIC RPI4_IO_REMAPPING_STRUCTURE Iort = {
> +  {
> +    ACPI_HEADER (EFI_ACPI_6_0_IO_REMAPPING_TABLE_SIGNATURE,
> +                 RPI4_IO_REMAPPING_STRUCTURE,
> +                 EFI_ACPI_IO_REMAPPING_TABLE_REVISION),
> +    1,                                              // NumNodes
> +    sizeof (EFI_ACPI_6_0_IO_REMAPPING_TABLE),       // NodeOffset
> +    0                                               // Reserved
> +  }, {
> +    // XHCI named component node
> +    {
> +      {
> +        EFI_ACPI_IORT_TYPE_NAMED_COMP,
> +        sizeof (RPI4_NC_NODE),
> +        0x0,
> +        0x0,
> +        0x0,
> +        0x0,
> +      },
> +      0x0,
> +      0x0,
> +      0x0,
> +      0x0,
> +      0x0,
> +      31,
> +    }, {
> +      "\\_SB_.SCB0.XHC0"
> +    }
> +  }
> +};
> +
> +#pragma pack()
> +
> +VOID* CONST ReferenceAcpiTable = &Iort;
> -- 
> 2.17.1
>