[PATCH v2 08/15] drm/i915: Fix region start during initial plane readout

[Andrzej Hajda]

On 15.12.2023 11:59, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> On MTL the stolen region starts at offset 8MiB from the start of
> LMEMBAR. The dma addresses are thus also offset by 8MiB. However the
> mm_node/etc. is zero based, and i915_pages_create_for_stolen() will
> add the appropriate region.start into the sg dma address. So when
> we do the readout we need to convert the dma address read from
> the PTE to be zero based as well.
> 
> Note that currently we don't take this path on MTL, but we should
> and thus this needs to be fixed. For lmem this works correctly
> already as the lmem region.start==0.
> 
> While at it let's also make sure the address points to somewhere within
> the memory region. We don't need to check the size as
> i915_gem_object_create_region_at() should later fail if the object size
> exceeds the region size.
> 
> Cc: Paz Zcharya <pazz at chromium.org>
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/display/intel_plane_initial.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_plane_initial.c b/drivers/gpu/drm/i915/display/intel_plane_initial.c
> index ffc92b18fcf5..db594ccf0323 100644
> --- a/drivers/gpu/drm/i915/display/intel_plane_initial.c
> +++ b/drivers/gpu/drm/i915/display/intel_plane_initial.c
> @@ -79,16 +79,18 @@ initial_plane_vma(struct drm_i915_private *i915,
>   		 * We don't currently expect this to ever be placed in the
>   		 * stolen portion.
>   		 */
> -		if (phys_base >= resource_size(&mem->region)) {
> +		if (phys_base < mem->region.start || phys_base > mem->region.end) {

Maybe better:
phys_base + fb_size > mem->region.end" ?
Btw it seems redundant with later checks in 
i915_gem_object_create_region_at.
IMO at this moment we need only check if "phys_base -= 
mem->region.start" makes sense.

Regards
Andrzej


>   			drm_err(&i915->drm,
> -				"Initial plane programming using invalid range, phys_base=%pa\n",
> -				&phys_base);
> +				"Initial plane programming using invalid range, phys_base=%pa (%s [%pa-%pa])\n",
> +				&phys_base, mem->region.name, &mem->region.start, &mem->region.end);
>   			return NULL;
>   		}
>   
>   		drm_dbg(&i915->drm,
>   			"Using phys_base=%pa, based on initial plane programming\n",
>   			&phys_base);
> +
> +		phys_base -= mem->region.start;
>   	} else {
>   		phys_base = base;
>   		mem = i915->mm.stolen_region;