On 22/08/2018 16:22, Lionel Landwerlin wrote:
On 22/08/2018 16:17, Tvrtko Ursulin wrote:
On 22/08/2018 16:08, Lionel Landwerlin wrote:
On 22/08/2018 15:29, Tvrtko Ursulin wrote:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
According to the documentation, when programming the subslice count
power-
gating configuration register, the value to be written into it on
Gen9LP
should actually in the format of:
1 slice = 0x001
2 slices = 0x010
3 slices = 0x100
s/slice/subslice/
Also 0b001 etc... Not hexadecimal.
Oops, you're right.
And not the popcount of the enabled subslice mask as on other
platforms.
So on Gen9LP platforms we have been programming 0x11 into those
bits, but
the documentation does not explain what would that achieve. Could it be
that we enable only two subslice on three sub-slice parts? Or hardware
simply ignores it and sticks with the maximum configuration?
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Bspec: 12247
---
Could this actually be true or I am severely misreading the docs? It
does
not sound plausible to me this would have been missed all this time..
How to test in what configuration do these parts run before and
after this
patch?
---
drivers/gpu/drm/i915/intel_lrc.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c
b/drivers/gpu/drm/i915/intel_lrc.c
index 36050f085071..cdfa962a1975 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -2508,9 +2508,15 @@ make_rpcs(struct drm_i915_private *dev_priv)
}
if (INTEL_INFO(dev_priv)->sseu.has_subslice_pg) {
+ u8 val;
+
+ val = hweight8(INTEL_INFO(dev_priv)->sseu.subslice_mask[0]);
+
+ if (IS_GEN9_LP(dev_priv))
+ val = BIT(val - 1);
Hmm... Are you breaking the 2 subslices setting here then?
(2 subslices = 0b10 which should be equal to hweight8(subslice_mask)
if I'm thinking right)
No and yes, I think.
subslice_mask = 0b011 => hweight = 2 => BIT(2 - 1) = BIT(1) = 0b010
into the register
In the same way, all together:
subslice_mask = 0b001 => hweight = 1 => BIT(0) = 0b001
subslice_mask = 0b011 => hweight = 2 => BIT(1) = 0b010
subslice_mask = 0b111 => hweight = 3 => BIT(2) = 0b100
Have I made a mistake somewhere?
Ah, yes! You're right :)
My eyes got tricked, thanks for finding this out.
At least half of the credit goes to you for linking to 12247 in scope of
one different thread!
With the comment fixed :
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@xxxxxxxxx>
Thanks!
Any ideas on how to test this? I'd like to commit message to be more
precise - have we been running with one slice too few? Or hardware
ignores the undocumented bit combination? Or even, is the documentation
perhaps incorrect?!
Regards,
Tvrtko
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