Damien Zammit <dam...@zamaudio.com> writes:
> + /* Enable ACPI */
> + outb(acpi_en, smi_cmd);
> + for (i = 0; i < 300; i++)
> + {
> + if ( (inw(pm1a_ctl) & SCI_EN) == SCI_EN)
> + break;
> + }
Perhaps this code should first check whether the SCI_EN bit is
already set, as described in ACPI 5.0 section 4.8.2.5
"Legacy/ACPI Select and the SCI Interrupt", and skip the outb if
so. Section 5.2.9 "Fixed ACPI Description Table (FADT)" says the
SMI_CMD field of FADT can be zero.
> + /* try sleep state 5 first */
> + outw(SLP_TYP5 | SLP_EN, pm1a_ctl);
> +
> + /* if we reach here then above did not work */
> + outw(SLP_TYP0 | SLP_EN, pm1a_ctl);
More about these below.
> +#define SLP_TYP0 (0x0 << 10)
> +#define SLP_TYP5 (0x5 << 10)
This hardcodes QEMU-specific values. ACPI 5.0 section 7.3.4 says
the values for PM1a_CNT.SLP_TYP must be read from the \S0-\S5
objects. The DSDT of my laptop has:
Name (_S5, Package (0x04) // _S5_: S5 System State
{
0x07,
Zero,
Zero,
Zero
})
so PM1a_CNT.SLP_TYP on this system should be 7, not 5. However,
implementing this properly would require an AML interpreter; the
DSDT of my laptop also has:
If (LEqual (S3DS, One))
{
Name (_S3, Package (0x04) // _S3_: S3 System State
{
0x05,
Zero,
Zero,
Zero
})
}
and defines S3DS as a field in an OperationRegion, so OSPM
would have to understand those concepts in order to know
whether \_S3 exists. I assume a similar construct is possible
for \_S5.
Maybe it's good enough if S5 works on QEMU. In that case though,
I would like to see a comment warning about this limitation.
