On 3/19/19 9:19 PM, Schmauss, Erik wrote:
-----Original Message-----
From: Maximilian Luz [mailto:luzmaximilian@xxxxxxxxx]
Sent: Tuesday, March 19, 2019 9:30 AM
To: Schmauss, Erik <erik.schmauss@xxxxxxxxx>; Moore, Robert
<robert.moore@xxxxxxxxx>; Wysocki, Rafael J
<rafael.j.wysocki@xxxxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx; devel@xxxxxxxxxx
Subject: Re: PROBLEM: Calling ObjectType on buffer field reports type
integer
On 3/18/19 11:28 PM, Schmauss, Erik wrote:
-----Original Message-----
From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi-
owner@xxxxxxxxxxxxxxx] On Behalf Of Schmauss, Erik
Sent: Thursday, March 14, 2019 10:19 AM
To: Maximilian Luz <luzmaximilian@xxxxxxxxx>; Moore, Robert
<robert.moore@xxxxxxxxx>; Wysocki, Rafael J
<rafael.j.wysocki@xxxxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx; devel@xxxxxxxxxx
Subject: RE: PROBLEM: Calling ObjectType on buffer field reports
type
integer
-----Original Message-----
From: Maximilian Luz [mailto:luzmaximilian@xxxxxxxxx]
Sent: Thursday, March 14, 2019 7:24 AM
To: Moore, Robert <robert.moore@xxxxxxxxx>; Schmauss, Erik
<erik.schmauss@xxxxxxxxx>; Wysocki, Rafael J
<rafael.j.wysocki@xxxxxxxxx>
Cc: linux-acpi@xxxxxxxxxxxxxxx; devel@xxxxxxxxxx
Subject: PROBLEM: Calling ObjectType on buffer field reports type
integer
Hi all,
it seems that buffer fields (created via CreateField) are
incorrectly reported as being of type integer (via ObjectType)
when
they are
small
enough to allow for that.
As far as I know all kernel versions are affected by this, I have
specifically checked 5.0 (5.0.2), 4.20, 4.19 and 4.18.
In more detail: On the Microsoft Surface Book 2, Surface Pro
(2017),
Surface Pro 6, Surface Laptop and Surface Laptop 2 devices there
is
the following piece of AML code:
Local0 = ^^_SAN.RQST (0x02, One, One, Zero, One)
If ((ObjectType (Local0) != 0x03))
{
// Error path
}
Else
{
// Success path
}
Which executes a command (RQST) and then checks the type of
the
returned field to determine if that command was successful (i.e.
returned a buffer object) or failed (i.e. returned any other type,
including integer). The buffer field that is being returned by RQST
is crated as
follows:
CreateField (RQBF, 0x20, Local3, ARB)
Local4 = ARB /* \_SB_._SAN.RQSX.ARB_ */
...
Return (Local4)
If the returned buffer field is small enough (smaller than
acpi_gbl_integer_byte_width), the error-path will always be
executed.
The full DSDT for the Surface Book 2 can be found here:
https://github.com/qzed/surfacebook2-
dsdt/blob/fa0ca7c7cba8fb0da1e79c282f9a9f4a12eaaa17/dsdt.dsl#L153
96
I have attached a patch (for 5.0) that fixes this issue and has been
in use on the affected devices for a few months now via
https://github.com/qzed/linux-surfacegen5-acpi and
https://github.com/jakeday/linux-surface/
I'm not aware of any issues regarding the patch, but then again
this
has, to my knowledge, only been tested on Microsoft Surface
devices.
I'll take a look at this and test the behavior on windows OS. Surface
laptops tend to have interesting firmware that expose these
differences.
I decided to run the following code on windows
Name (BUF1, Buffer() {0x32, 0x56, 0x12, 0xff, 0x12, 0xd1, 0xd0,
0xd6, 0x54})
Name (BUF2, Buffer(0x09) {})
Method (DS00)
{
CreateField (BUF1, 1, 1, FLD0)
local0 = FLD0
return (ObjectType(Local0))
}
Method (DS01)
{
CreateField (BUF1, 0, 72, FLD1)
local1 = FLD1
return (ObjectType(Local1))
}
Method (DS02)
{
CreateField (BUF2, 0, 72, FLD2)
local2 = FLD2
return (ObjectType(Local2))
}
Here's an output from windbg
AMLI(? for help)-> run \ds00
run \ds00
\DS00 completed successfully with object data:
Integer(:Value=0x3[3])
AMLI(? for help)-> run \ds01
run \ds01
\DS01 completed successfully with object data:
Integer(:Value=0x3[3])
AMLI(? for help)-> run \ds02
run \ds02
\DS02 completed successfully with object data:
Integer(:Value=0x3[3])
AMLI(? for help)->
So it does seem like windows AML interpreter is doing what you
expect it to do.
After I applied your patch with a small modification below and it
causes some regressions in our AML test suite. I would like to take
time to look at each of these to make sure that all of the behavioral
Differences are expected. Bob will be back in the office so I'll discuss
this with him as well.
Thank you for the update!
I mainly choose this solution because it was the first one I came up
with, I'm not that experienced with acpica so yours may very well be
better. What I found a bit odd though and why I stuck with this
solution was that AML_FIELD_ACCESS_BUFFER did not seem to be
used anywhere (in contrast to the other field access types).
I've tried your modification. However, just replacing the check with
obj_desc->common.type == ACPI_TYPE_BUFFER_FIELD
did seem to break things for me, but I may be missing something.
More specifics on what is being broken: The communication via the
OperationRegion does not seem to work properly any more. There is a
Yeah, that's what I was thinking... After discussions with Bob, this whole
Behavior is an issue with Winodws AML interpreter not following the spec.
Page 927 of ACPI 6.3 specification states the following:
"If the Buffer Field is smaller than or equal to the size of an Integer (in bits), it will be treated as an Integer. Otherwise, it will be treated as a Buffer."
So windows is not following this rule here. This rule is also the same for
field units so our next step is to check windows behavior for this. It would
be nice to file a bug against windows but they've never responded to these
reports in the past....
For the record, windows does detect the object type of CreateField correctly.
Method (SS02)
{
CreateField (BUF2, 0, 72, FLD2)
return (ObjectType(FLD2))
}
This method returns 0xE as expected.
Thanks for the reference. Indeed looks like Microsoft is doing their own
thing here, I should have figured as much. How are things like this
being handled? Adopt Microsoft's behavior?
Maximilian
status flag in the communication buffer that should get cleared and it
looks like it isn't. My current theory is:
The flag being checked is a byte field in the communication buffer,
created via CreateByteField (RQBF, 0x00, VSTS). Thus it should have
type ACPI_TYPE_BUFFER_FIELD (?). Due to this, your change seems to
create a buffer instead of an integer object in
acpi_ex_read_data_from_field.
When this field is now evaluated for the communication check via
If ((VSTS == Zero)) { /* success */ } Else { /* failure */ }
the check in acpi_ex_do_logical_op exmisc.c converts the second
argument to a buffer of size acpi_gbl_integer_byte_width. The buffer
sizes are then different as VSTS has size 1 and thus the check fails,
getting misinterpreted as communication-failure.
Maximilian
Thanks,
Erik
Erik
Maximilian
Signed-off-by: Maximilian Luz <luzmaximilian@xxxxxxxxx>
---
drivers/acpi/acpica/dsopcode.c | 2 +-
drivers/acpi/acpica/exfield.c | 12 +++++++++---
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/acpi/acpica/dsopcode.c
b/drivers/acpi/acpica/dsopcode.c index
78f9de260d5f..0cd858520f5b
100644
--- a/drivers/acpi/acpica/dsopcode.c
+++ b/drivers/acpi/acpica/dsopcode.c
@@ -123,7 +123,7 @@ acpi_ds_init_buffer_field(u16
aml_opcode,
/* Offset is in bits, count is in bits */
- field_flags = AML_FIELD_ACCESS_BYTE;
+ field_flags = AML_FIELD_ACCESS_BUFFER;
bit_offset = offset;
bit_count = (u32) length_desc->integer.value;
diff --git a/drivers/acpi/acpica/exfield.c
b/drivers/acpi/acpica/exfield.c index e5798f15793a..55abd9e035a0
100644
--- a/drivers/acpi/acpica/exfield.c
+++ b/drivers/acpi/acpica/exfield.c
@@ -98,6 +98,7 @@ acpi_ex_read_data_from_field(struct
acpi_walk_state *walk_state,
union acpi_operand_object *buffer_desc;
void *buffer;
u32 buffer_length;
+ u8 field_flags;
ACPI_FUNCTION_TRACE_PTR(ex_read_data_from_field,
obj_desc);
@@ -146,11 +147,16 @@ acpi_ex_read_data_from_field(struct
acpi_walk_state *walk_state,
* Note: Field.length is in bits.
*/
buffer_length =
- (acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc-
field.bit_length);
+ (acpi_size)ACPI_ROUND_BITS_UP_TO_BYTES(obj_desc-
common_field.bit_length);
+ field_flags = obj_desc->common_field.field_flags;
- if (buffer_length > acpi_gbl_integer_byte_width) {
+ if (buffer_length > acpi_gbl_integer_byte_width ||
+ (field_flags & AML_FIELD_ACCESS_TYPE_MASK) ==
+AML_FIELD_ACCESS_BUFFER) {
Rather than using field_flags at all, we can do something like
if ((BufferLength > AcpiGbl_IntegerByteWidth) || (ObjDesc-
Common.Type
== ACPI_TYPE_BUFFER_FIELD))
This will restrict translations to the CreateField but your solution
might also be valid...
I'll run a few more test cases tomorrow.
- /* Field is too large for an Integer, create a Buffer
instead */
+ /*
+ * Field is either too large for an Integer, or a actually of
type
+ * buffer, so create a Buffer.
+ */
buffer_desc =
acpi_ut_create_buffer_object(buffer_length);
if (!buffer_desc) {
--
2.20.1
