Allow dcp interchange to scanout interchange compressed by oliverbestmann · Pull Request #449 · AsahiLinux/linux

oliverbestmann · 2026-02-07T21:18:14Z

Works together with this mesa MR:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39755

Conan-Kudo

The UAPI change needs to be separately contributed to Linux directly, not this fork.

See this documentation: https://docs.kernel.org/process/submitting-patches.html

jannau · 2026-02-07T21:55:31Z

include/uapi/drm/drm_fourcc.h

 */
 #define DRM_FORMAT_MOD_APPLE_GPU_TILED fourcc_mod_code(APPLE, 1)
 #define DRM_FORMAT_MOD_APPLE_GPU_TILED_COMPRESSED fourcc_mod_code(APPLE, 2)
+#define DRM_FORMAT_MOD_APPLE_INTERCHANGE_COMPRESSED fourcc_mod_code(APPLE, 3)


For experimenting we should move this into the driver with

#ifndef DRM_FORMAT_MOD_APPLE_INTERCHANGE_COMPRESSED #define DRM_FORMAT_MOD_APPLE_INTERCHANGE_COMPRESSED fourcc_mod_code(APPLE, 3) #endif

I'm not sure if we want one or more APPLE_INTERCHANGE_COMPRESSED modifiers to handle YCbCr formats which use 32x32 tiles for Y

Is this enough of a difference to warrant a new format modifier? If the tile size only changes for the luma channel of Y'CbCr textures, can we not just handle that by checking is_yuv for the framebuffer format info struct? E.g.

tile_w = fb->format->is_yuv ? 32 : 16

waltmck · 2026-02-23T06:31:58Z

Thank you for the exciting work!

I tested this with nixos-apple-silicon 6.10 using your flake, on an M2 Macbook Air. Hyprland fails to launch with the following repeated log message:

kernel: apple-dcp 231c00000.dcp: swap failed! status 4
kernel: dcp: plane 0 modifiers: c00000000000003
kernel: apple-dcp 231c00000.dcp: RTKit: syslog message: UPPipe.cpp:3920: IOMFB verify_uc_surface: Planesize insufficient for data plane size 17039360, data size 17301504
kernel: apple-dcp 231c00000.dcp: RTKit: syslog message: UPPipeDCP_H13P.cpp:4554: bool IOMFB::UPPipeDCP_H13P::verify_surfaces(IOMFB::SwapRequest *): Error with the interchange surface
kernel: apple-dcp 231c00000.dcp: RTKit: syslog message: FramebufferDCP.cpp:2175: AppleCLCD: verify_swap failed for swap id: 4285

oliverbestmann · 2026-02-24T11:31:12Z

@waltmck

I tested this with nixos-apple-silicon 6.10 using your flake, on an M2 Macbook Air.

~~Thank you. Is that with the notch enabled or disabled? And what's your selected display resolution?~~

It was not working with hyprland on my machine too. I've fixed the issue now. Please try again with the latest update to the flake.

waltmck · 2026-02-25T00:30:13Z

@waltmck

I tested this with nixos-apple-silicon 6.10 using your flake, on an M2 Macbook Air.

~~Thank you. Is that with the notch enabled or disabled? And what's your selected display resolution?~~

It was not working with hyprland on my machine too. I've fixed the issue now. Please try again with the latest update to the flake.

With your latest flake I can run Hyprland (and I've been using it to work for the last few hours without issues). Is there an easy way to check with certainty that compressed scanout is actually being used?

oliverbestmann · 2026-02-25T12:27:43Z

You can use drm_info to see that modifier c00000000000003 is used for the plane.

waltmck · 2026-02-25T14:28:46Z

You can use drm_info to see that modifier c00000000000003 is used for the plane.

yep, I do see that so it seems to be working.

drivers/gpu/drm/apple/plane.c

jannau · 2026-03-01T10:41:16Z

the code misses a check to ensure the computed surface size for interchange framebuffers fits into the framebuffer's reported buffer size

oliverbestmann · 2026-03-01T10:47:22Z

the code misses a check to ensure the computed surface size for interchange framebuffers fits into the framebuffer's reported buffer size

Whats the expected behavior in that case? assert and kernel panic, or some logging and quietly ignoring the plane?

jannau · 2026-03-01T11:04:47Z

the code misses a check to ensure the computed surface size for interchange framebuffers fits into the framebuffer's reported buffer size

Whats the expected behavior in that case? assert and kernel panic, or some logging and quietly ignoring the plane?

check needs to happen in atomic_check where it can fail, possible that there there are drm_format helpers for that using driver specific formats (I would have to check myself)

chadmed · 2026-03-01T12:34:40Z

Tested as mostly-working on G14G, G14S and G13S, however overlays are broken on kwin. May be size/alignment related, as fractional scaling factors and certain cursor images (notably the Breeze I-beam) cause framebuffer creation to fail. This is most obvious with the cursor, but may occur with other oddly-sized overlay framebuffers.

oliverbestmann · 2026-03-01T12:50:23Z

Tested as mostly-working on G14G, G14S and G13S, however overlays are broken on kwin. May be size/alignment related, as fractional scaling factors and certain cursor images (notably the Breeze I-beam) cause framebuffer creation to fail. This is most obvious with the cursor, but may occur with other oddly-sized overlay framebuffers.

Thank you. I had no problems running this with kde. I'll try to reproduce the issues as soon as I can.

Signed-off-by: Oliver Bestmann <oliver.bestmann@googlemail.com>

jannau · 2026-03-02T19:42:42Z

drivers/gpu/drm/apple/plane.c

+	 * The metadata buffer contains 8 bytes per 16x16 compression tile.
+         * Addressing is fully twiddled, so both width and height are padded to
+         * powers-of-two.
+         */


the comment from the drm_fourcc.h description would be more more appropriate:

/* * ... The metadata section rounds the image dimensions to * powers-of-two and contains 8 bytes for each 16x16 compression subtile. * Subtiles are interleaved (Morton order). */

It's the most up to date description.

jannau · 2026-03-02T19:51:17Z

drivers/gpu/drm/apple/plane.c

+         * Addressing is fully twiddled, so both width and height are padded to
+         * powers-of-two.
+         */
+	unsigned w_tl = DIV_ROUND_UP(roundup_pow_of_two(width), 16);


isn't this the same as as roundup_pow_of_two(tw)?

jannau · 2026-03-02T19:51:28Z

drivers/gpu/drm/apple/plane.c

+static struct apple_interchange_layout
+get_apple_interchange_layout(u32 width, u32 height, u32 bpp)
+{
+	const u32 cacheline = 0x80;


please use a define

jannau · 2026-03-02T19:53:01Z

drivers/gpu/drm/apple/plane.c

+
+	u32 tw = DIV_ROUND_UP(width, 16);
+	u32 th = DIV_ROUND_UP(height, 16);
+	u32 tsize_B = 16 * 16 * (bpp / 8);


this should use DIV_ROUND_UP(bpp, 8), not that it matters right now.
That would still be for bit-packed formats. Not sure if dcp supports those or if we want to use them, probably not.
Single component formats with 10- or 12-bit per pixel are more common. Possible that drm_format_info_bpp() includes the padding though.

oliverbestmann force-pushed the asahi-dcp-interchange branch from 2d2ee37 to d14c2b6 Compare February 7, 2026 21:19

Conan-Kudo requested changes Feb 7, 2026

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jannau reviewed Feb 7, 2026

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jannau force-pushed the asahi-wip branch 2 times, most recently from 0031cb6 to 79a307d Compare February 14, 2026 20:09

oliverbestmann force-pushed the asahi-dcp-interchange branch from d14c2b6 to 605fc30 Compare February 22, 2026 15:07

oliverbestmann force-pushed the asahi-dcp-interchange branch 3 times, most recently from 368641c to cdeaea6 Compare February 24, 2026 11:19

jannau reviewed Feb 28, 2026

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jannau force-pushed the asahi-wip branch from 79a307d to 7457799 Compare March 1, 2026 10:29

jannau force-pushed the asahi-wip branch from 7457799 to 89c915d Compare March 1, 2026 16:43

drm/apple: support interchange compression

0ddf41f

Signed-off-by: Oliver Bestmann <oliver.bestmann@googlemail.com>

oliverbestmann force-pushed the asahi-dcp-interchange branch from cdeaea6 to 0ddf41f Compare March 2, 2026 18:00

oliverbestmann changed the base branch from asahi-wip to asahi March 2, 2026 18:03

jannau reviewed Mar 2, 2026

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