[PATCH 1/1][SRU][H] platform/x86: intel_pmc_core: Ignore GBE LTR on Tiger Lake platforms

[AceLan Kao]

From: "David E. Box" <david.e.box at linux.intel.com>

BugLink: https://bugs.launchpad.net/bugs/1919116

Due to a HW limitation, the Latency Tolerance Reporting (LTR) value
programmed in the Tiger Lake GBE controller is not large enough to allow
the platform to enter Package C10, which in turn prevents the platform from
achieving its low power target during suspend-to-idle.  Ignore the GBE LTR
value on Tiger Lake. LTR ignore functionality is currently performed solely
by a debugfs write call. Split out the LTR code into its own function that
can be called by both the debugfs writer and by this work around.

Signed-off-by: David E. Box <david.e.box at linux.intel.com>
Reviewed-by: Sasha Neftin <sasha.neftin at intel.com>
Cc: intel-wired-lan at lists.osuosl.org
Reviewed-by: Rajneesh Bhardwaj <irenic.rajneesh at gmail.com>
Link: https://lore.kernel.org/r/20210319201844.3305399-2-david.e.box@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
(cherry picked from commit d1635448f1105e549b4041aab930dbc6945fc635)
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao at canonical.com>
---
 drivers/platform/x86/intel_pmc_core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
index 260d49dca1ad..765f15edfe24 100644
--- a/drivers/platform/x86/intel_pmc_core.c
+++ b/drivers/platform/x86/intel_pmc_core.c
@@ -1277,6 +1277,15 @@ static int pmc_core_probe(struct platform_device *pdev)
 		pmc_core_send_ltr_ignore(3);
 	}
 
+	/*
+	 * On TGL, due to a hardware limitation, the GBE LTR blocks PC10 when
+	 * a cable is attached. Tell the PMC to ignore it.
+	 */
+	if (pmcdev->map == &tgl_reg_map) {
+		dev_dbg(&pdev->dev, "ignoring GBE LTR\n");
+		pmc_core_send_ltr_ignore(3);
+	}
+
 	pmc_core_dbgfs_register(pmcdev);
 
 	device_initialized = true;
-- 
2.25.1