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drivers/tpm/ppi: Fix generated ACPI

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The SSDT contains:
    CreateByteField (PPOP, Local0, TPPF)

However, CreateByteField requires the source argument to be
(Buffer | String | Integer).  PPOP is an OperationRegion, so
iasl correctly reports:

    Error 6058 - Invalid type ([Region] found)

Per ACPI spec, OperationRegions must use CreateField rather than
CreateByteField. Replace the AML emission with:

    CreateField (PPOP, Local0 * 8, 8, TPPF)

This reads one byte at an arbitrary offset inside the PPI
OpRegion and is fully standards-compliant. This isn't a
functional change, just "correct".

Test=boot starbook_mtl, verify iasl can decompile and recompile
SSDT and TPM is still operational.

Change-Id: If80bb5bf69562f8b904c1b315e95a0b5627efbc4
Signed-off-by: Sean Rhodes <sean@starlabs.systems>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84606
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
This commit is contained in:
Sean Rhodes 2024-09-30 21:22:13 +01:00 • committed by Matt DeVillier
commit ac5c57d24a
1 changed files with 17 additions and 4 deletions
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21
src/drivers/tpm/ppi.c
View file

@ -633,7 +633,10 @@ void tpm_ppi_acpi_fill_ssdt(const struct device *dev)
*/
acpigen_write_method_serialized("FUNC", 1);
/* Local0 = ToInteger(Arg0) */
acpigen_write_to_integer(ARG0_OP, LOCAL0_OP);
/* If (Local0 > 0x80) */
acpigen_write_if();
acpigen_emit_byte(LGREATER_OP);
acpigen_emit_byte(LOCAL0_OP);
@ -641,17 +644,27 @@ void tpm_ppi_acpi_fill_ssdt(const struct device *dev)
acpigen_write_return_integer(0);
acpigen_pop_len(); /* If */
/* TPPF = CreateField("PPOP", Local0) */
acpigen_emit_byte(CREATE_BYTE_OP);
acpigen_emit_namestring("PPOP");
/* Local1 = (Local0 * 0x08) */
acpigen_emit_byte(MULTIPLY_OP);
acpigen_emit_byte(LOCAL0_OP);
acpigen_write_integer(8);
acpigen_emit_byte(LOCAL1_OP);
/* CreateField (PPOP, Local1, 0x08, TPPF) */
acpigen_emit_ext_op(CREATEFIELD_OP);
acpigen_emit_namestring("PPOP");
acpigen_emit_byte(LOCAL1_OP);
acpigen_write_integer(8);
/* Name of the dynamically-created field */
acpigen_emit_namestring("TPPF");
/* Local0 = ToInteger("TPPF") */
/* Local0 = ToInteger(TPPF) */
acpigen_emit_byte(TO_INTEGER_OP);
acpigen_emit_namestring("TPPF");
acpigen_emit_byte(LOCAL0_OP);
/* Return (Local0) */
acpigen_write_return_op(LOCAL0_OP);
acpigen_pop_len(); /* Method */