Re: [Intel-gfx] [PATCH 09/10] drm/i915: turn on small BAR support

["Das, Nirmoy" <nirmoy.das@linux.intel.com>]

On 6/21/2022 10:38 AM, Matthew Auld wrote:
> On 17/06/2022 13:33, Thomas Hellström wrote:
>>
>> On 5/25/22 20:43, Matthew Auld wrote:
>>> With the uAPI in place we should now have enough in place to ensure a
>>> working system on small BAR configurations.
>>>
>>> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
>>> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
>>> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
>>> Cc: Jon Bloomfield <jon.bloomfield@intel.com>
>>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>>> Cc: Jordan Justen <jordan.l.justen@intel.com>
>>> Cc: Kenneth Graunke <kenneth@whitecape.org>
>>> Cc: Akeem G Abodunrin <akeem.g.abodunrin@intel.com>
>>> ---
>>>   drivers/gpu/drm/i915/gt/intel_region_lmem.c | 10 ++++------
>>>   1 file changed, 4 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c 
>>> b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
>>> index e9c12e0d6f59..6c6f8cbd7321 100644
>>> --- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
>>> +++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
>>> @@ -111,12 +111,6 @@ static struct intel_memory_region 
>>> *setup_lmem(struct intel_gt *gt)
>>>           flat_ccs_base = intel_gt_read_register(gt, 
>>> XEHPSDV_FLAT_CCS_BASE_ADDR);
>>>           flat_ccs_base = (flat_ccs_base >> XEHPSDV_CCS_BASE_SHIFT) 
>>> * SZ_64K;
>>> -        /* FIXME: Remove this when we have small-bar enabled */
>>> -        if (pci_resource_len(pdev, 2) < lmem_size) {
>>> -            drm_err(&i915->drm, "System requires small-BAR support, 
>>> which is currently unsupported on this kernel\n");
>>> -            return ERR_PTR(-EINVAL);
>>> -        }
>>> -
>>>           if (GEM_WARN_ON(lmem_size < flat_ccs_base))
>>>               return ERR_PTR(-EIO);
>>> @@ -169,6 +163,10 @@ static struct intel_memory_region 
>>> *setup_lmem(struct intel_gt *gt)
>>>       drm_info(&i915->drm, "Local memory available: %pa\n",
>>>            &lmem_size);
>>> +    if (io_size < lmem_size)
>>> +        drm_info(&i915->drm, "Using a reduced BAR size of %lluMiB. 
>>> Consider enabling the full BAR size if available in the BIOS.\n",
>>> +             (u64)io_size >> 20);
>>> +
>>
>> Hmm. I wonder what BIOS uis typically call the mappable portion of 
>> VRAM. I'll se if I can check that on my DG1 system. Might be that an 
>> average user misinterprets "full BAR".
>
> "PCI Subsystem settings" -> "Above 4G memory [enabled/disabled]"
>
> Sample size of one though.
>
> Maybe s/full BAR size/full memory size/ ?


Or  s/full BAR size/re-sizable BAR/

In newer BIOS, there is a more direct option to enable re-sizable bar: 
"Re-Size BAR"/"Resizable BAR".


Nirmoy

>
>>
>> /Thomas
>>
>>
>>
>>>       return mem;
>>>   err_region_put: