[PATCH v2 0/2] drm: Add DRM driver for GlandaGPU (VHDL soft-IP GPU)

[Leander Kieweg <kieweg.leander@gmail.com>]

This is v2 of the GlandaGPU DRM driver series [1], addressing review
feedback from Thomas Zimmermann, Conor Dooley, Uwe Kleine-König, and
the automated review bot on v1.

GlandaGPU is a small VHDL soft-IP 2D display controller, currently
targeting a Terasic DE10-Standard (Cyclone V SoC). This series has
been tested both against a QEMU digital twin and on real hardware.

Hardware/VHDL:    https://github.com/stiangglanda/GlandaGPU
QEMU fork:        https://github.com/stiangglanda/qemu-glandagpu
Userspace tests:  https://github.com/stiangglanda/GlandaGPU-userspace-tests

Changes since v1:

dt-bindings:
- add a link to the GlandaGPU project in the binding description
- add clocks to the required properties
- fix the example to use interrupt-parent and the GIC_SPI/
  IRQ_TYPE_LEVEL_HIGH macros instead of raw numbers
- fix missing trailing newline

driver core:
- drop the struct device *dev field, use drm_device.dev instead
- open-code drm_encoder_init() instead of drm_simple_encoder_init(),
  which is being phased out
- switch the plane update path from manual dma_resv_lock()/
  drm_gem_shmem_vmap_locked() to DRM_GEM_SHADOW_PLANE_HELPER_FUNCS/
  DRM_GEM_SHADOW_PLANE_FUNCS. This also fixes sleeping calls being
  made from atomic-commit context and a raw map.vaddr dereference,
  both flagged by automated review
- use drm_gem_fb_create_with_dirty() instead of a custom fb_create
  implementation
- remove the redundant new_state == NULL check in the CRTC flush
  helper
- remove the ioctl-based UAPI (CLEAR/RECT/LINE) entirely. As Thomas
  pointed out in v1, fixed-function 2D ioctls aren't a good fit for
  mainline DRM, and userspace rendering into the shadow-plane
  framebuffer covers the same functionality
- fix a double drm_mode_config_cleanup() call in the probe and
  remove error paths (devres already handles this)
- call drm_atomic_helper_shutdown() on remove
- fix a teardown race where in-flight work could touch already
  unmapped MMIO, using drm_dev_unplug()/drm_dev_enter()/
  drm_dev_exit()
- move IRQ registration to after CRTC initialization, avoiding a
  potential NULL pointer dereference from an early-firing shared IRQ
- fix platform_get_irq() error handling. Negative error codes such
  as -EPROBE_DEFER were previously misread as "no IRQ available"

new in v2:
- add PCI probe support alongside the existing platform_driver/
  devicetree path, backed by a matching QEMU device model, so the
  driver can be tested against a virtual device without needing
  devicetree or real hardware. Real hardware continues to use the
  platform_driver path unchanged. This replaces the old x86 test
  device patch 3/3, reducing the series from 3 to 2 patches.

Known open item: the QEMU test device currently uses a placeholder
ID from the range QEMU reserves for experimental, unregistered use
(1af4:10f0, see [2]). I've requested a permanent
ID from Gerd Hoffmann and will post a follow-up once it's assigned.

[1] https://lore.kernel.org/dri-devel/20260714101146.200416-1-kieweg.leander@gmail.com/T/#t
[2] https://www.qemu.org/docs/master/specs/pci-ids.html

Leander Kieweg (2):
  dt-bindings: display: Add GlandaGPU binding
  drm/glanda: Add initial DRM driver for GlandaGPU

 .../bindings/display/glanda,gpu.yaml          |  55 ++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 MAINTAINERS                                   |   6 +
 drivers/gpu/drm/tiny/Kconfig                  |  11 +
 drivers/gpu/drm/tiny/Makefile                 |   1 +
 drivers/gpu/drm/tiny/glandagpu.c              | 579 ++++++++++++++++++
 6 files changed, 654 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/glanda,gpu.yaml
 create mode 100644 drivers/gpu/drm/tiny/glandagpu.c

-- 
2.43.0