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

[Thomas Hellström]

On Tue, 2022-06-21 at 11:05 +0200, Das, Nirmoy wrote:
> 
> 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 at intel.com>
> > > > Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> > > > Cc: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> > > > Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> > > > Cc: Jon Bloomfield <jon.bloomfield at intel.com>
> > > > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> > > > Cc: Jordan Justen <jordan.l.justen at intel.com>
> > > > Cc: Kenneth Graunke <kenneth at whitecape.org>
> > > > Cc: Akeem G Abodunrin <akeem.g.abodunrin at 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".

A quick googling turns up "Resizable BAR". My Asus Bios on the DG1
machine says "ReSize BAR (Resizable BAR support to harness full GPU
memory)".

So "Resizable BAR" should hopefully be understood by most people. Not
sure though if this is the same as "Above 4G memory", although the
latter must be a prerequisite I assume. 

/Thomas



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