Re: [Intel-gfx] [PATCH 1/2] drm/i915/gt: Do not use stolen on MTL

[Nirmoy Das]

Hi Oak,

On 7/4/2023 5:01 PM, Zeng, Oak wrote:

Hi Nirmoy,

The changes in this series make sense to me. I searched my code base, there are 
a few other places where stolen memory is allocated:

Thanks for checking all the places.

1) intel_dpt_create: I don't know what is dpt. Should we also consider this 
one? Maybe we never read from cpu?

This expects i915_ggtt_has_aperture() which MTL doesn't have.

2) create_ring_vma: I think cpu only write ring buffer but never read it. So 
should be okay.

Same as above.

3) vlv_rc6_init

This  seems to be only for IS_VALLEYVIEW().

4) there are a few places calling 
i915_gem_object_create_stolen_for_preallocated. I think this is also stolen 
memory?

Where is this from, do you mean I915_BO_PREALLOC ?

For integrated gpu like MTL, do we use stolen memory for ggtt? If yes, does CPU 
only write ggtt/never read?

GTT pages only seems to be written.


Thanks,

Nirmoy

Thanks,
Oak

-----Original Message-----
From: Das, Nirmoy <nirmoy....@intel.com>
Sent: June 30, 2023 1:02 PM
To: intel-gfx@lists.freedesktop.org
Cc: Das, Nirmoy <nirmoy....@intel.com>; Zeng, Oak <oak.z...@intel.com>; Jani
Nikula <jani.nik...@linux.intel.com>; Joonas Lahtinen
<joonas.lahti...@linux.intel.com>; Andi Shyti <andi.sh...@linux.intel.com>;
Hajda, Andrzej <andrzej.ha...@intel.com>
Subject: [PATCH 1/2] drm/i915/gt: Do not use stolen on MTL

Use smem on MTL due to a HW bug in MTL that prevents
reading from stolen memory using LMEM BAR.

Cc: Oak Zeng <oak.z...@intel.com>
Cc: Jani Nikula <jani.nik...@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
Cc: Andi Shyti <andi.sh...@linux.intel.com>
Cc: Andrzej Hajda <andrzej.ha...@intel.com>
Signed-off-by: Nirmoy Das <nirmoy....@intel.com>
---
  drivers/gpu/drm/i915/gt/intel_gt.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c
b/drivers/gpu/drm/i915/gt/intel_gt.c
index 33a61046ba58..9f64d61dd5fc 100644
--- a/drivers/gpu/drm/i915/gt/intel_gt.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt.c
@@ -466,7 +466,7 @@ static int intel_gt_init_scratch(struct intel_gt *gt, 
unsigned
int size)
        obj = i915_gem_object_create_lmem(i915, size,
                                          I915_BO_ALLOC_VOLATILE |
                                          I915_BO_ALLOC_GPU_ONLY);
-       if (IS_ERR(obj))
+       if (IS_ERR(obj) && !IS_METEORLAKE(i915)) /* Wa_22018444074 */
                obj = i915_gem_object_create_stolen(i915, size);
        if (IS_ERR(obj))
                obj = i915_gem_object_create_internal(i915, size);
--
2.39.0