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drivers/intel/gma/acpi: Reduce display switching stubs

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_DCS, _DGS and _DSS are required by specification. However,
we never implemented them properly, and no OS driver com-
plained yet. So we stub them out and keep the traditional
behavior in case an OS driver checks for their existence.

The old implementations also only returned static values as
there never was any write to their GNVS variables. The TRAP()
that was called in one place is actually implemented by some
ThinkPad's SMI handler as docking event. However, as the call
precedes these SMI handlers in coreboot history, it's most
likely an accident.

Change-Id: Ib0b9fcdd58df254d3b2290900e3bc206a7abd92d
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39726
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
This commit is contained in:
Nico Huber
2020-03-21 18:40:03 +01:00
committed by Patrick Georgi
parent cc85ce0aa0
commit e98f6af77b
15 changed files with 28 additions and 99 deletions
Download Patch File Download Diff File Expand all files Collapse all files

41
src/drivers/intel/gma/acpi.c
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@@ -102,39 +102,38 @@ drivers_intel_gma_displays_ssdt_generate(const struct i915_gpu_controller_info *
}
/*
Method(_DCS, 0)
{
Return (^^XDCS(<device number>))
}
* _DCS, _DGS and _DSS are required by specification. However,
* we never implemented them properly, and no OS driver com-
* plained yet. So we stub them out and keep the traditional
* behavior in case an OS driver checks for their existence.
*/
/*
Method(_DCS, 0)
{
Return (0x1d)
}
*/
acpigen_write_method("_DCS", 0);
acpigen_emit_byte(0xa4); /* ReturnOp. */
acpigen_emit_namestring("^^XDCS");
acpigen_write_byte(i);
acpigen_write_return_integer(0x1d);
acpigen_pop_len();
/*
Method(_DGS, 0)
{
Return (^^XDGS(<device number>))
}
Method(_DGS, 0)
{
Return (0)
}
*/
acpigen_write_method("_DGS", 0);
acpigen_emit_byte(0xa4); /* ReturnOp. */
acpigen_emit_namestring("^^XDGS");
acpigen_write_byte(i);
acpigen_write_return_integer(0);
acpigen_pop_len();
/*
Method(_DSS, 1)
{
^^XDSS(0x5a, Arg0)
}
Method(_DSS, 1)
{
}
*/
acpigen_write_method("_DSS", 1);
acpigen_emit_namestring("^^XDSS");
acpigen_write_byte(i);
acpigen_emit_byte(0x68); /* Arg0Op. */
acpigen_pop_len();
acpigen_pop_len();