Hi Fenghua,

On 11/18/25 04:03, Fenghua Yu wrote:

Hi, Ben,

On 11/17/25 08:59, Ben Horgan wrote:

quoted

In actbl2.h, acpi_pptt_cache describes the fields in the original
Cache Type Structure. In PPTT table version 3 a new field was added at
the
end, cache_id. This is described in acpi_pptt_cache_v1 but rather than
including all v1 fields it just includes this one.

In lieu of this being fixed in acpica, introduce
acpi_pptt_cache_v1_full to
contain all the fields of the Cache Type Structure . Update the existing
code to use this new struct. This simplifies the code and removes a
non-standard use of ACPI_ADD_PTR.

Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
I have opened a pull request to acpica to update acpi_pptt_cache_v1 to
include all fields. https://github.com/acpica/acpica/pull/1059

Change since v4:
Use fields directly in acpi_pptt_cache_v1_full
Delay the casting

Changes since v3:
New patch
---
  drivers/acpi/pptt.c | 47 +++++++++++++++++++++++++++++++++++----------
  1 file changed, 37 insertions(+), 10 deletions(-)

diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
index 2856254e29d7..53fde9bd8140 100644
--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c

@@ -21,6 +21,25 @@

  #include <linux/cacheinfo.h>
  #include <acpi/processor.h>
  +/*
+ * The acpi_pptt_cache_v1 in actbl2.h, which is imported from acpica,
+ * only contains the cache_id field rather than all the fields of the
+ * Cache Type Structure. Use this alternative structure until it is
+ * resolved in acpica.
+ */
+struct acpi_pptt_cache_v1_full {
+    struct acpi_subtable_header header;
+    u16 reserved;
+    u32 flags;
+    u32 next_level_of_cache;
+    u32 size;
+    u32 number_of_sets;
+    u8 associativity;
+    u8 attributes;
+    u16 line_size;
+    u32 cache_id;
+};

Should "__packed" be added to this table?

Yes, I missed that.

Should this table be defined in include/acpi/actbl2.h? Seems defining
the two cache tables separately in two places are not natural?

Indeed. The dificulty is that include/acpi/actbl2.h is generated from
acpica. I propose a fix for this in the  pull request mentioned above:
https://github.com/acpica/acpica/pull/1059 This extends
acpi_pptt_cache_v1 to include all the fields in the new version of the
cache type structure (not just cache_id).

One thing I could do if it looks like the acpica change will be accepted
is to temporarily delete acpi_pptt_cache_v1 from include/acpi/actbl2.h
and rename acpi_pptt_cache_v1_full in drivers/acpi/pptt.c to
acpi_pptt_cache_v1. When include/acpi/actbl2.h is updated the conflict
should be evident and the version in drivers/acpi/pptt.c can be dropped.
 I'll keep it like it is for now though as this would be an api breaking
change for acpica and the maintainers may prefer to handle this a
different way.

Thanks.

-Fenghua

Thanks,

Ben