Change in coreboot[master]: soc/intel/tigerlake: Add empty _DSM for TCSS DMA devices

[Duncan Laurie (Code Review)]

Duncan Laurie has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/46641 )

Change subject: soc/intel/tigerlake: Add empty _DSM for TCSS DMA devices
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soc/intel/tigerlake: Add empty _DSM for TCSS DMA devices

This empty _DSM is required for the SOC to properly enter S0ix.  The
same empty _DSM exists for the TCSS XHCI and PCIe root port devices in
the DSDT so just I just declared it here for consistency rather than
putting it in the SSDT.

BUG=b:171310928
TEST=authorize PCI tunnel on TBT dock and ensure that the system can
still enter S0ix and the residency counter increases.

Signed-off-by: Duncan Laurie 
Change-Id: I016b07c5b497b06ded1e2c81ec149e3d0fc161bb
---
M src/soc/intel/tigerlake/acpi/tcss_dma.asl
1 file changed, 5 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/41/46641/1

diff --git a/src/soc/intel/tigerlake/acpi/tcss_dma.asl b/src/soc/intel/tigerlake/acpi/tcss_dma.asl
index 085990d..e8e2d0e 100644
--- a/src/soc/intel/tigerlake/acpi/tcss_dma.asl
+++ b/src/soc/intel/tigerlake/acpi/tcss_dma.asl
@@ -92,3 +92,8 @@
 {
    Return (Package() { 0x6D, 4 })
 }
+
+Method (_DSM, 4, Serialized)
+{
+	Return (Buffer() { 0 })
+}

[Duncan Laurie (Code Review)]

Duncan Laurie has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/46641 )

Change subject: soc/intel/tigerlake: Add empty _DSM for TCSS DMA devices
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Patch Set 1:

Hm actually I remember now why I removed the _DSM from the DMA device: it gets added by the SSDT for the retimer.

When testing this I was using the chromium tree which had not yet submitted the retimer patch so it was not creating the _DSM and s0ix wasn't working.  Once that patch landed it works.

For now we do not need this patch, but this needs to be handled cleaner somehow for both _DSD and _DSM since there can be only one defined per device and ideally we'd support the PCI _DSM properly.

[Duncan Laurie (Code Review)]

Duncan Laurie has abandoned this change. ( https://review.coreboot.org/c/coreboot/+/46641 )

Change subject: soc/intel/tigerlake: Add empty _DSM for TCSS DMA devices
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Abandoned