mb/google/brya/acpi: Fix GC6 entry and exit sequences

Now that the virtual wire situation is figured out, the GC6 sequence
is updated to match the latest HW design guide from Nvidia. This
allows Nvidia test software to (mostly) successfully execute the GC6
test, but with some PCIe AER errors.

BUG=b:214581763
TEST=tested with Nvidia test software

Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Change-Id: Ia094c4fa9b4db094a59b9b6f02be1a649ee8569b
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66641
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Ivy Jian <ivy.jian@quanta.corp-partner.google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

1 files changed, 17 insertions, 30 deletions

diff --git a/src/mainboard/google/brya/acpi/power.asl b/src/mainboard/google/brya/acpi/power.asl
index bb2bc3514b..55f8dbda8f 100644
--- a/src/mainboard/google/brya/acpi/power.asl
+++ b/src/mainboard/google/brya/acpi/power.asl
@@ -54,30 +54,26 @@ Method (GC6I, 0, Serialized)
 	/* Put PCIe link into L2/3 */
 	\_SB.PCI0.PEG0.DL23 ()
 
-	/* Assert GPU_PERST_L */
-	\_SB.PCI0.CTXS (GPIO_GPU_PERST_L)
+	/* Wait for GPU to deassert its GPIO4, i.e. GPU_NVVDD_EN */
+	GPPL (GPIO_GPU_NVVDD_EN, 0, 20)
 
 	/* Deassert PG_GPU_ALLRAILS */
 	\_SB.PCI0.CTXS (GPIO_GPU_ALLRAILS_PG)
 
-	/* Deassert EN_PP0950_GPU_X */
+	/* Ramp down PEXVDD */
 	\_SB.PCI0.CTXS (GPIO_PEXVDD_PWR_EN)
-
-	/* Wait for de-assertion of PG_PP0950_GPU */
 	GPPL (GPIO_PEXVDD_PG, 0, 20)
-
-	/* Wait for GPU to deassert GPU_NVVDD_EN */
-	GPPL (GPIO_GPU_NVVDD_EN, 0, 20)
+	Sleep (10)
 
 	/* Deassert EN_PPVAR_GPU_NVVDD */
 	\_SB.PCI0.CTXS (GPIO_NVVDD_PWR_EN)
-
-	/* Wait for de-assertion of PG_PPVAR_GPU_NVVDD */
 	GPPL (GPIO_NVVDD_PG, 0, 20)
+	Sleep (2)
 
-	/* Deassert EN_PCH_PPVAR_GPU_FBVDDQ (active-low) */
-	\_SB.PCI0.STXS (GPIO_FBVDD_PWR_EN)
+	/* Assert GPU_PERST_L */
+	\_SB.PCI0.CTXS (GPIO_GPU_PERST_L)
 
+	Printf ("dGPU entered GC6")
 	GC6E = GC6_STATE_ENTERED
 }
 
@@ -89,33 +85,24 @@ Method (GC6O, 0, Serialized)
 	/* Deassert GPU_PERST_L */
 	\_SB.PCI0.STXS (GPIO_GPU_PERST_L)
 
-	/* Put PCIe link into L0 state */
-	\_SB.PCI0.PEG0.LD23 ()
-
 	/* Wait for GPU to assert GPU_NVVDD_EN */
 	GPPL (GPIO_GPU_NVVDD_EN, 1, 20)
 
-	/*
-	 * There is a 4ms window once the GPU asserts GPU_NVVDD_EN to
-	 * perform the following:
-	 * 1. Enable GPU_NVVDD
-	 * 2. Enable GPU_PEX
-	 * 3. Wait for all PG
-	 * 4. Assert FBVDD (active-low)
-	 * At the end of the 4ms window, the GPU will deassert its
-	 * GPIO1_GC6_FB_EN signal that is used to keep the FBVDD
-	 * rail up during GC6.
-	 */
-	 \_SB.PCI0.STXS (GPIO_NVVDD_PWR_EN)
-	 Stall (20)
+	/* Ramp up NVVDD */
+	\_SB.PCI0.STXS (GPIO_NVVDD_PWR_EN)
+	GPPL (GPIO_NVVDD_PG, 1, 4)
+
+	/* Ramp up PEXVDD */
 	 \_SB.PCI0.STXS (GPIO_PEXVDD_PWR_EN)
-	 GPPL (GPIO_NVVDD_PG, 1, 4)
 	 GPPL (GPIO_PEXVDD_PG, 1, 4)
-	 \_SB.PCI0.CTXS (GPIO_FBVDD_PWR_EN)
 
 	/* Assert PG_GPU_ALLRAILS */
 	\_SB.PCI0.STXS (GPIO_GPU_ALLRAILS_PG)
 
+	/* Put PCIe link into L0 state */
+	\_SB.PCI0.PEG0.LD23 ()
+
+	Printf ("dGPU exited GC6")
 	GC6E = GC6_STATE_EXITED
 }