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

["Andrei Warkentin" <awarkentin@vmware.com>]

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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.

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

A
________________________________
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>
---
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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


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