Re: [Intel-gfx] [PATCH 1/3] drm/i915: Set I915_BO_ALLOC_USER for framebuffer

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Mar 06, 2023 at 05:22:19PM +0100, Das, Nirmoy wrote:
> 
> On 3/6/2023 3:21 PM, Ville Syrjälä wrote:
> > On Mon, Mar 06, 2023 at 11:28:48AM +0100, Nirmoy Das wrote:
> >> Framebuffer is exposed to userspace so set I915_BO_ALLOC_USER
> >> flag for it. This also make sure that ttm allocates offset
> >> for lmem objects.
> > I have no idea what that means.
> 
> Sorry for poor explanation.
> 
> Without I915_BO_ALLOC_USER, ttm will assume the obj as kernel buffer and 
> will not allocate fake offset which I needed for fb_mmap callback to work.

So that's the fake vm_pgoff thing? Doesn't that exist just so
mmap() through /dev/dri* can be passed a "gem handle"? 
With fbdev mmap we already know which BO we want to map so
why would any of that stuff even be needed?

> 
> Regards,
> Nirmoy
> 
> >
> >> Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
> >> ---
> >>   drivers/gpu/drm/i915/display/intel_dpt.c           | 4 +++-
> >>   drivers/gpu/drm/i915/display/intel_fbdev.c         | 3 ++-
> >>   drivers/gpu/drm/i915/display/intel_plane_initial.c | 3 ++-
> >>   3 files changed, 7 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/display/intel_dpt.c b/drivers/gpu/drm/i915/display/intel_dpt.c
> >> index ad1a37b515fb..2e6238881860 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_dpt.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_dpt.c
> >> @@ -254,7 +254,9 @@ intel_dpt_create(struct intel_framebuffer *fb)
> >>   
> >>   	size = round_up(size * sizeof(gen8_pte_t), I915_GTT_PAGE_SIZE);
> >>   
> >> -	dpt_obj = i915_gem_object_create_lmem(i915, size, I915_BO_ALLOC_CONTIGUOUS);
> >> +	dpt_obj = i915_gem_object_create_lmem(i915, size,
> >> +					      I915_BO_ALLOC_CONTIGUOUS |
> >> +					      I915_BO_ALLOC_USER);
> >>   	if (IS_ERR(dpt_obj) && i915_ggtt_has_aperture(to_gt(i915)->ggtt))
> >>   		dpt_obj = i915_gem_object_create_stolen(i915, size);
> >>   	if (IS_ERR(dpt_obj) && !HAS_LMEM(i915)) {
> >> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> >> index 3659350061a7..98ae3a3a986a 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> >> @@ -163,7 +163,8 @@ static int intelfb_alloc(struct drm_fb_helper *helper,
> >>   	obj = ERR_PTR(-ENODEV);
> >>   	if (HAS_LMEM(dev_priv)) {
> >>   		obj = i915_gem_object_create_lmem(dev_priv, size,
> >> -						  I915_BO_ALLOC_CONTIGUOUS);
> >> +						  I915_BO_ALLOC_CONTIGUOUS |
> >> +						  I915_BO_ALLOC_USER);
> >>   	} else {
> >>   		/*
> >>   		 * If the FB is too big, just don't use it since fbdev is not very
> >> diff --git a/drivers/gpu/drm/i915/display/intel_plane_initial.c b/drivers/gpu/drm/i915/display/intel_plane_initial.c
> >> index bb6ea7de5c61..4a3680f6a3f5 100644
> >> --- a/drivers/gpu/drm/i915/display/intel_plane_initial.c
> >> +++ b/drivers/gpu/drm/i915/display/intel_plane_initial.c
> >> @@ -110,7 +110,8 @@ initial_plane_vma(struct drm_i915_private *i915,
> >>   	    size * 2 > i915->dsm.usable_size)
> >>   		return NULL;
> >>   
> >> -	obj = i915_gem_object_create_region_at(mem, phys_base, size, 0);
> >> +	obj = i915_gem_object_create_region_at(mem, phys_base, size,
> >> +					       I915_BO_ALLOC_USER);
> >>   	if (IS_ERR(obj))
> >>   		return NULL;
> >>   
> >> -- 
> >> 2.39.0

-- 
Ville Syrjälä
Intel