Re: [Intel-gfx] [PATCH v2 2/2] drm/i915/display: Do not use stolen on MTL

[Andrzej Hajda <andrzej.hajda@intel.com>]

On 13.07.2023 16:45, Nirmoy Das wrote:
>
> On 7/12/2023 12:06 AM, Nirmoy Das wrote:
>> Use smem on MTL due to a HW bug in MTL that prevents
>> reading from stolen memory using LMEM BAR.
>>
>> v2: improve stolen skip detection(Andrzej)
>>
>> Cc: Oak Zeng <oak.zeng@intel.com>
>> Cc: Jani Nikula <jani.nikula@linux.intel.com>
>> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
>> Cc: Andi Shyti <andi.shyti@linux.intel.com>
>> Cc: Andrzej Hajda <andrzej.hajda@intel.com>
>> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
>> Reviewed-by: Oak Zeng <oak.zeng@intel.com>
>> Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
>> Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_fbdev.c   | 5 ++++-
>>   drivers/gpu/drm/i915/display/intel_overlay.c | 5 +++--
>>   2 files changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c 
>> b/drivers/gpu/drm/i915/display/intel_fbdev.c
>> index 1cc0ddc6a310..e019bbcd474e 100644
>> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
>> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
>> @@ -187,8 +187,11 @@ static int intelfb_alloc(struct drm_fb_helper 
>> *helper,
>>            * If the FB is too big, just don't use it since fbdev is 
>> not very
>>            * important and we should probably use that space with FBC 
>> or other
>>            * features.
>> +         *
>> +         * Also skip stolen on MTL as Wa_22018444074 mitigation.
>>            */
>> -        if (size * 2 < dev_priv->dsm.usable_size)
>> +        if (size * 2 < dev_priv->dsm.usable_size ||
>> +            !(IS_METEORLAKE(dev_priv)))
>
> Just realized  this is wrong, stolen will be picked on non-mtl even if 
> the stolen usable size is < 2*size which is not expected.

if (!(IS_METEORLAKE(dev_priv)) && size * 2 < dev_priv->dsm.usable_size) ?

Regards
Andrzej

>
> I will keep this as v1
>
>
> Regards,
>
> Nirmoy
>
>>               obj = i915_gem_object_create_stolen(dev_priv, size);
>>           if (IS_ERR(obj))
>>               obj = i915_gem_object_create_shmem(dev_priv, size);
>> diff --git a/drivers/gpu/drm/i915/display/intel_overlay.c 
>> b/drivers/gpu/drm/i915/display/intel_overlay.c
>> index d6fe2bbabe55..09c1aa1427ad 100644
>> --- a/drivers/gpu/drm/i915/display/intel_overlay.c
>> +++ b/drivers/gpu/drm/i915/display/intel_overlay.c
>> @@ -1348,11 +1348,12 @@ int intel_overlay_attrs_ioctl(struct 
>> drm_device *dev, void *data,
>>   static int get_registers(struct intel_overlay *overlay, bool use_phys)
>>   {
>>       struct drm_i915_private *i915 = overlay->i915;
>> -    struct drm_i915_gem_object *obj;
>> +    struct drm_i915_gem_object *obj = ERR_PTR(-ENODEV);
>>       struct i915_vma *vma;
>>       int err;
>>   -    obj = i915_gem_object_create_stolen(i915, PAGE_SIZE);
>> +    if (!IS_METEORLAKE(i915)) /* Wa_22018444074 */
>> +        obj = i915_gem_object_create_stolen(i915, PAGE_SIZE);
>>       if (IS_ERR(obj))
>>           obj = i915_gem_object_create_internal(i915, PAGE_SIZE);
>>       if (IS_ERR(obj))