Re: [PATCH v3 19/26] drm/{i915/xe}/writeback: Add a writeback helper to get ggtt address

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 25 Mar 2026, Suraj Kandpal <suraj.kandpal@intel.com> wrote:
> We need the ggtt address offset to write in the WD_SURF register.
> With i915_vma being defined in xe and i915 and both having different
> ways to extract the address this poses an issue.
> Add a helper so that correct function is called to extract address
> depending on xe/i915 driver.
>
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>  drivers/gpu/drm/i915/Makefile                       |  1 +
>  drivers/gpu/drm/i915/display/intel_writeback.c      |  3 ++-
>  .../gpu/drm/i915/display/intel_writeback_helper.c   | 12 ++++++++++++
>  .../gpu/drm/i915/display/intel_writeback_helper.h   |  8 ++++++++
>  drivers/gpu/drm/xe/Makefile                         |  3 ++-
>  drivers/gpu/drm/xe/display/xe_writeback_helper.c    | 13 +++++++++++++
>  6 files changed, 38 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/gpu/drm/i915/display/intel_writeback_helper.c
>  create mode 100644 drivers/gpu/drm/i915/display/intel_writeback_helper.h
>  create mode 100644 drivers/gpu/drm/xe/display/xe_writeback_helper.c
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 1e9140e7713c..a1023de728e5 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -316,6 +316,7 @@ i915-y += \
>  	display/intel_vga.o \
>  	display/intel_wm.o \
>  	display/intel_writeback.o \
> +	display/intel_writeback_helper.o \
>  	display/skl_prefill.o \
>  	display/skl_scaler.o \
>  	display/skl_universal_plane.o \
> diff --git a/drivers/gpu/drm/i915/display/intel_writeback.c b/drivers/gpu/drm/i915/display/intel_writeback.c
> index c79e7330b81c..d3c3716a28a9 100644
> --- a/drivers/gpu/drm/i915/display/intel_writeback.c
> +++ b/drivers/gpu/drm/i915/display/intel_writeback.c
> @@ -1,6 +1,6 @@
>  // SPDX-License-Identifier: MIT
>  /*
> - * Copyright © 2025 Intel Corporation
> + * Copyright © 2026 Intel Corporation

You need to set this once, correctly, instead of changing mid-series.

>   */
>  
>  #include <linux/slab.h>
> @@ -25,6 +25,7 @@
>  #include "intel_display_utils.h"
>  #include "intel_fb_pin.h"
>  #include "intel_writeback.h"
> +#include "intel_writeback_helper.h"
>  #include "intel_writeback_reg.h"
>  
>  struct intel_writeback_connector {
> diff --git a/drivers/gpu/drm/i915/display/intel_writeback_helper.c b/drivers/gpu/drm/i915/display/intel_writeback_helper.c
> new file mode 100644
> index 000000000000..f483ed6ffc6b
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/display/intel_writeback_helper.c
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#include "i915_vma.h"
> +#include "intel_writeback_helper.h"
> +
> +u32 intel_get_ggtt_addr(struct i915_vma *vma)
> +{
> +	return i915_ggtt_offset(vma);
> +}

Please let's not add more stuff that we need to fix up later. This is
counter-productive to separating display from i915 and xe.

> diff --git a/drivers/gpu/drm/i915/display/intel_writeback_helper.h b/drivers/gpu/drm/i915/display/intel_writeback_helper.h
> new file mode 100644
> index 000000000000..b46f437c3875
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/display/intel_writeback_helper.h
> @@ -0,0 +1,8 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +struct i915_vma;
> +
> +u32 intel_get_ggtt_addr(struct i915_vma *vma);
> diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
> index 2e456070895a..4483e97153ba 100644
> --- a/drivers/gpu/drm/xe/Makefile
> +++ b/drivers/gpu/drm/xe/Makefile
> @@ -224,7 +224,8 @@ xe-$(CONFIG_DRM_XE_DISPLAY) += \
>  	display/xe_initial_plane.o \
>  	display/xe_panic.o \
>  	display/xe_stolen.o \
> -	display/xe_tdf.o
> +	display/xe_tdf.o \
> +	display/xe_writeback_helper.o
>  
>  # Display code shared with i915
>  xe-$(CONFIG_DRM_XE_DISPLAY) += \
> diff --git a/drivers/gpu/drm/xe/display/xe_writeback_helper.c b/drivers/gpu/drm/xe/display/xe_writeback_helper.c
> new file mode 100644
> index 000000000000..5898984b129c
> --- /dev/null
> +++ b/drivers/gpu/drm/xe/display/xe_writeback_helper.c
> @@ -0,0 +1,13 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2026 Intel Corporation
> + */
> +
> +#include "xe_ggtt.h"
> +#include "xe_display_vma.h"
> +#include "intel_writeback_helper.h"
> +
> +u32 intel_get_ggtt_addr(struct i915_vma *vma)
> +{
> +	return lower_32_bits(xe_ggtt_node_addr(vma->node));
> +}

-- 
Jani Nikula, Intel