From 62c52eac1ad680fc68ef6d75955127dca46e2740 Mon Sep 17 00:00:00 2001
From: Anshuman Gupta <anshuman.gupta@intel.com>
Date: Fri, 14 Oct 2022 17:02:58 +0530
Subject: [PATCH] drm/i915/dgfx: Keep PCI autosuspend control 'on' by default on all dGPU
Git-commit: 62c52eac1ad680fc68ef6d75955127dca46e2740
Patch-mainline: v6.1-rc3
Alt-commit: 66eb93e71a7a6695b7c5eb682e3ca1c980cf9d58
References: git-fixes
DGFX platforms has lmem and cpu can access the lmem objects
via mmap and i915 internal i915_gem_object_pin_map() for
i915 own usages. Both of these methods has pre-requisite
requirement to keep GFX PCI endpoint in D0 for a supported
iomem transaction over PCI link. (Refer PCIe specs 5.3.1.4.1)
Both DG1/DG2 have a known hardware bug that violates the PCIe specs
and support the iomem read write transaction over PCIe bus despite
endpoint is D3 state.
Due to above H/W bug, we had never observed any issue with i915 runtime
PM versus lmem access.
But this issue becomes visible when PCIe gfx endpoint's upstream
bridge enters to D3, at this point any lmem read/write access will be
returned as unsupported request. But again this issue is not observed
on every platform because it has been observed on few host machines
DG1/DG2 endpoint's upstream bridge does not bind with pcieport driver.
which really disables the PCIe power savings and leaves the bridge
at D0 state.
We need a unique interface to read/write from lmem with runtime PM
wakeref protection something similar to intel_uncore_{read, write},
keep autosuspend control to 'on' on all discrete platforms,
until we have a unique interface to read/write from lmem.
This just change the default autosuspend setting of i915 on dGPU,
user can still change it to 'auto'.
V2:
- Modified the commit message and subject with more information.
- Changed the Fixes tag to LMEM support commit. [Joonas]
- Changed !HAS_LMEM() Cond to !IS_DGFX(). [Rodrigo]
Fixes: b908be543e44 ("drm/i915: support creating LMEM objects")
Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014113258.1284226-1-anshuman.gupta@intel.com
(cherry picked from commit 66eb93e71a7a6695b7c5eb682e3ca1c980cf9d58)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/intel_runtime_pm.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 6ed5786bcd29..744cca507946 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -591,8 +591,15 @@ void intel_runtime_pm_enable(struct intel_runtime_pm *rpm)
pm_runtime_use_autosuspend(kdev);
}
- /* Enable by default */
- pm_runtime_allow(kdev);
+ /*
+ * FIXME: Temp hammer to keep autosupend disable on lmem supported platforms.
+ * As per PCIe specs 5.3.1.4.1, all iomem read write request over a PCIe
+ * function will be unsupported in case PCIe endpoint function is in D3.
+ * Let's keep i915 autosuspend control 'on' till we fix all known issue
+ * with lmem access in D3.
+ */
+ if (!IS_DGFX(i915))
+ pm_runtime_allow(kdev);
/*
* The core calls the driver load handler with an RPM reference held.
--
2.35.3