RE: [RFC PATCH v2 1/8] ACPICA: IORT: Update for revision E | linux-acpi

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-----Original Message-----
From: Lorenzo Pieralisi <redacted>
Sent: Tuesday, March 23, 2021 8:54 AM
To: Kaneda, Erik <redacted>
Cc: Shameerali Kolothum Thodi <redacted>;
linux-arm-kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
iommu@lists.linux-foundation.org; devel@acpica.org; Moore, Robert
[off-list ref]; Linuxarm [off-list ref];
steven.price@arm.com; Sami.Mujawar@arm.com; robin.murphy@arm.com;
wanghuiqiang [off-list ref]
Subject: Re: [RFC PATCH v2 1/8] ACPICA: IORT: Update for revision E

On Mon, Mar 22, 2021 at 09:57:58PM +0000, Kaneda, Erik wrote:

-----Original Message-----
From: Shameerali Kolothum Thodi
[off-list ref]
Sent: Monday, March 22, 2021 3:36 AM
To: Kaneda, Erik <redacted>; linux-arm-
kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
iommu@lists.linux-
foundation.org; devel@acpica.org; Lorenzo Pieralisi
[off-list ref]; Moore, Robert
[off-list ref]
Cc: Linuxarm <redacted>; steven.price@arm.com;
Sami.Mujawar@arm.com; robin.murphy@arm.com; wanghuiqiang
[off-list ref]
Subject: [Devel] Re: [RFC PATCH v2 1/8] ACPICA: IORT: Update for
revision E
[+]

Hi Erik,

As this is now just merged ino acpica-master and based on the discussion
we
had here,

https://github.com/acpica/acpica/pull/638

I had a discussion with ARM folks(Lorenzo) in the linaro-open-discussions
call
and
can confirm that the IORT Revision E is not the final specification and has
some issues
which is now corrected in the latest E.b revision[1]. Also there are no
current
users
for the Rev E and it may not be a good idea to push this version into the
Linux
kernel
or elsewhere.

So could you please revert the merge and I am planning to work on the
E.b
soon.
Hi,

Please let me know if I need to explicitly send a revert pull request or not.
Please send a revert pull request and I'll remember to not submit Linux-ize
the IORT patches.
From all of the activity that I've seen with the IORT specification,
it looks like this table is nontrivial to design and maintain. The
difficulty I have with the table is that I do not understand which
table revisions are in active use.
Hi Lorenzo,

Possibly all of them in firmware in the field - I am not sure what you
are asking though; if you can elaborate I'd be grateful.
Yes, I'd be happy to explain.

The ACPICA project contains code that provides definitions for ACPI tables. After each release of this project, the codebase gets translated to a Linux style syntax and relevant patches are submitted to Linux so that it can use these table definitions in their driver codebase. From ACPICA's perspective, the code providing these definitions are used to implement a compiler/disassembler called iASL. This tool disassembles table definitions so that the user doesn't have to open a hex editor to decipher ACPI tables. Our goal with iASL is to be able to disassemble as many ACPI tables as possible to give users the ability to compile and debug ACPI tables.

Out of the 60+ tables that we support, IORT has been tricky to maintain. There are revisions A-E and we have received pull requests from engineers from ARM or companies that work with ARM. We are grateful of their contributions but some of these pull requests have broken support for earlier versions of IORT. In addition, we sometimes receive communication from people like Shameer saying that revision E does not currently have users. This leaves Bob and I very confused about which revisions we should be focused on supporting in iASL.

We need your help in understanding which versions of IORT should be supported by iASL as well as Linux.

I hope this helps.. Let me know if you need me to clarify anything that I've written.

Thanks,
Erik

So my question is this: which IORT revisions are being actively used?
See above.

Thanks,
Lorenzo

Thanks,
Erik
Thanks,
Shameer

1. https://developer.arm.com/documentation/den0049/latest/

-----Original Message-----
From: iommu [mailto:iommu-bounces@lists.linux-foundation.org] On
Behalf Of
Shameer Kolothum
Sent: 19 November 2020 12:12
To: linux-arm-kernel@lists.infradead.org; linux-acpi@vger.kernel.org;
iommu@lists.linux-foundation.org; devel@acpica.org
Cc: Linuxarm <redacted>; steven.price@arm.com;
Guohanjun
(Hanjun Guo) [off-list ref]; Sami.Mujawar@arm.com;
robin.murphy@arm.com; wanghuiqiang [off-list ref]
Subject: [RFC PATCH v2 1/8] ACPICA: IORT: Update for revision E

IORT revision E contains a few additions like,
    -Added an identifier field in the node descriptors to aid table
     cross-referencing.
    -Introduced the Reserved Memory Range(RMR) node. This is used
     to describe memory ranges that are used by endpoints and requires
     a unity mapping in SMMU.
    -Introduced a flag in the RC node to express support for PRI.

Signed-off-by: Shameer Kolothum
[off-list ref]
---
 include/acpi/actbl2.h | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/include/acpi/actbl2.h b/include/acpi/actbl2.h index
ec66779cb193..274fce7b5c01 100644
--- a/include/acpi/actbl2.h
+++ b/include/acpi/actbl2.h
@@ -68,7 +68,7 @@
  * IORT - IO Remapping Table
  *
  * Conforms to "IO Remapping Table System Software on ARM
Platforms",
- * Document number: ARM DEN 0049D, March 2018
+ * Document number: ARM DEN 0049E, June 2020
  *

**********************************************************
******
**************/

@@ -86,7 +86,8 @@ struct acpi_iort_node {
 	u8 type;
 	u16 length;
 	u8 revision;
-	u32 reserved;
+	u16 reserved;
+	u16 identifier;
 	u32 mapping_count;
 	u32 mapping_offset;
 	char node_data[1];
@@ -100,7 +101,8 @@ enum acpi_iort_node_type {
 	ACPI_IORT_NODE_PCI_ROOT_COMPLEX = 0x02,
 	ACPI_IORT_NODE_SMMU = 0x03,
 	ACPI_IORT_NODE_SMMU_V3 = 0x04,
-	ACPI_IORT_NODE_PMCG = 0x05
+	ACPI_IORT_NODE_PMCG = 0x05,
+	ACPI_IORT_NODE_RMR = 0x06,
 };

 struct acpi_iort_id_mapping {
@@ -167,10 +169,10 @@ struct acpi_iort_root_complex {
 	u8 reserved[3];		/* Reserved, must be zero */
 };

-/* Values for ats_attribute field above */
+/* Masks for ats_attribute field above */

-#define ACPI_IORT_ATS_SUPPORTED         0x00000001	/* The root
complex supports ATS */
-#define ACPI_IORT_ATS_UNSUPPORTED       0x00000000	/* The root
complex doesn't support ATS */
+#define ACPI_IORT_ATS_SUPPORTED         (1)	/* The root complex
supports ATS */
+#define ACPI_IORT_PRI_SUPPORTED         (1<<1)	/* The root
complex
supports PRI */

 struct acpi_iort_smmu {
 	u64 base_address;	/* SMMU base address */
@@ -241,6 +243,17 @@ struct acpi_iort_pmcg {
 	u64 page1_base_address;
 };

+struct acpi_iort_rmr {
+	u32 rmr_count;
+	u32 rmr_offset;
+};
+
+struct acpi_iort_rmr_desc {
+	u64 base_address;
+	u64 length;
+	u32 reserved;
+};
+

/**********************************************************
*****
****************
  *
  * IVRS - I/O Virtualization Reporting Structure
--
2.17.1

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