[SRU][N:linux][PATCH 3/5] drm/i915/mtl: Wake GT before sending H2G message

[Thibault Ferrante]

From: Vinay Belgaumkar <vinay.belgaumkar at intel.com>

BugLink: https://bugs.launchpad.net/bugs/2117716

Instead of waiting until the interrupt reaches GuC, we can grab a
forcewake while triggering the H2G interrupt. GEN11_GUC_HOST_INTERRUPT
is inside sgunit and is not affected by forcewakes. However, there
could be some delays when platform is entering/exiting some higher
level platform sleep states and a H2G is triggered. A forcewake
ensures those sleep states have been fully exited and further
processing occurs as expected. The hysteresis timers for C6 and
higher sleep states will ensure there is no unwanted race between the
wake and processing of the interrupts by GuC.

This will have an official WA soon so adding a FIXME in the comments.

v2: Make the new ranges watertight to address BAT failures and update
commit message (Matt R).

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar at intel.com>
Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240119193513.221730-1-vinay.belgaumkar@intel.com
(cherry picked from commit 6d46d09a0d7dd412c5b76f74f89fe4448ba2117e)
Signed-off-by: Thibault Ferrante <thibault.ferrante at canonical.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index dfefad5a5fec9..76400e9c40f05 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1800,7 +1800,10 @@ static const struct intel_forcewake_range __mtl_fw_ranges[] = {
 	GEN_FW_RANGE(0x24000, 0x2ffff, 0), /*
 		0x24000 - 0x2407f: always on
 		0x24080 - 0x2ffff: reserved */
-	GEN_FW_RANGE(0x30000, 0x3ffff, FORCEWAKE_GT)
+	GEN_FW_RANGE(0x30000, 0x3ffff, FORCEWAKE_GT),
+	GEN_FW_RANGE(0x40000, 0x1901ef, 0),
+	GEN_FW_RANGE(0x1901f0, 0x1901f3, FORCEWAKE_GT)
+		/* FIXME: WA to wake GT while triggering H2G */
 };
 
 /*
-- 
2.48.1