[PATCH 09/10] drm/xe: Implement a helper for reading out a GGTT PTE at a specified offset

[Juha-Pekka Heikkilä]

Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila at gmail.com>

On Mon, May 5, 2025 at 3:20 PM Maarten Lankhorst <dev at lankhorst.se> wrote:
>
> Split the GGTT PTE readout to a separate function, this is useful for
> adding testcases in the next commit, and also cleaner than manually
> reading out GGTT.
>
> Signed-off-by: Maarten Lankhorst <dev at lankhorst.se>
> ---
>  drivers/gpu/drm/xe/display/xe_plane_initial.c |  6 +-----
>  drivers/gpu/drm/xe/xe_ggtt.c                  | 12 ++++++++++++
>  drivers/gpu/drm/xe/xe_ggtt.h                  |  1 +
>  3 files changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/display/xe_plane_initial.c b/drivers/gpu/drm/xe/display/xe_plane_initial.c
> index 6502b82741732..59b2ff2026d47 100644
> --- a/drivers/gpu/drm/xe/display/xe_plane_initial.c
> +++ b/drivers/gpu/drm/xe/display/xe_plane_initial.c
> @@ -87,12 +87,8 @@ initial_plane_bo(struct xe_device *xe,
>
>         base = round_down(plane_config->base, page_size);
>         if (IS_DGFX(xe)) {
> -               u64 __iomem *gte = tile0->mem.ggtt->gsm;
> -               u64 pte;
> +               u64 pte = xe_ggtt_read_pte(tile0->mem.ggtt, base);
>
> -               gte += base / XE_PAGE_SIZE;
> -
> -               pte = ioread64(gte);
>                 if (!(pte & XE_GGTT_PTE_DM)) {
>                         drm_err(&xe->drm,
>                                 "Initial plane programming missing DM bit\n");
> diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
> index 20d49a96c2407..2316f3a74d9c3 100644
> --- a/drivers/gpu/drm/xe/xe_ggtt.c
> +++ b/drivers/gpu/drm/xe/xe_ggtt.c
> @@ -912,3 +912,15 @@ u64 xe_ggtt_encode_pte_flags(struct xe_ggtt *ggtt,
>  {
>         return ggtt->pt_ops->pte_encode_flags(bo, pat_index);
>  }
> +
> +/**
> + * xe_ggtt_read_pte - Read a PTE from the GGTT
> + * @ggtt: &xe_ggtt
> + * @offset: the offset for which the mapping should be read.
> + *
> + * Used by testcases, and by display reading out an inherited bios FB.
> + */
> +u64 xe_ggtt_read_pte(struct xe_ggtt *ggtt, u64 offset)
> +{
> +       return ioread64(ggtt->gsm + (offset / XE_PAGE_SIZE));
> +}
> diff --git a/drivers/gpu/drm/xe/xe_ggtt.h b/drivers/gpu/drm/xe/xe_ggtt.h
> index 437ba65f33860..600a76526cf34 100644
> --- a/drivers/gpu/drm/xe/xe_ggtt.h
> +++ b/drivers/gpu/drm/xe/xe_ggtt.h
> @@ -50,5 +50,6 @@ void xe_ggtt_might_lock(struct xe_ggtt *ggtt);
>  #endif
>
>  u64 xe_ggtt_encode_pte_flags(struct xe_ggtt *ggtt, struct xe_bo *bo, u16 pat_index);
> +u64 xe_ggtt_read_pte(struct xe_ggtt *ggtt, u64 offset);
>
>  #endif
> --
> 2.45.2
>