[PATCH v2 0/7] drm/simpledrm: Support system memory framebuffers

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

Hi,

this series of patches adds support for framebuffers residing in system
memory to the simple-framebuffer DRM driver. To do this, the DT bindings
are extended do accept the memory-region property in addition to the reg
property for specifying the framebuffer memory. This is done because the
framebuffer memory will typically also need to be marked as reserved so
that the operating system will not reuse it and the memory-region
property is the standard property to reference reserved memory regions.

A new compatible string is documented to annotate the framebuffer memory
regions and the simpledrm driver has code added to bind such annotated
regions to the simple-framebuffer device.

The second half of the series then adds support for the XB24 and AB24
formats and ties it all together to provide a simple-framebuffer on
Jetson Xavier NX. It should be noted, though, that the Jetson Xavier NX
device tree nodes are placeholders only and it is expected that firmware
or a bootloader will fill these in at runtime, due to the variable
nature of the values that they contain.

This example also uses (but doesn't depend on) the iommu-addresses
property that has been proposed and which will hopefully be merged soon.

Version 1 of these patches can be found here:

	https://lore.kernel.org/all/20220905163300.391692-1-thierry.reding@gmail.com/

Changes in v2:
- DT fields are now cleared so that they can be filled in at runtime
- add XB24 support and treat AB24 the same (alpha bits are unused)
- consistently use struct iosys_map
- fix issues with DT bindings

I've tested these with a simple UEFI implementation that will fill in
the placeholder values and set the simple-framebuffer's status property
to "okay".

Thierry

Thierry Reding (7):
  dt-bindings: display: simple-framebuffer: Support system memory
    framebuffers
  dt-bindings: display: simple-framebuffer: Document 32-bit BGR format
  dt-bindings: reserved-memory: Support framebuffer reserved memory
  drm/simpledrm: Add support for system memory framebuffers
  drm/format-helper: Support the XB24 format
  drm/simpledrm: Support the XB24/AB24 format
  arm64: tegra: Add simple framebuffer on Jetson Xavier NX

 .../bindings/display/simple-framebuffer.yaml  |   7 +
 .../bindings/reserved-memory/framebuffer.yaml |  52 +++++
 .../nvidia/tegra194-p3509-0000+p3668-0001.dts |  33 ++++
 arch/arm64/boot/dts/nvidia/tegra194.dtsi      |   2 +-
 drivers/gpu/drm/drm_format_helper.c           |  37 ++++
 drivers/gpu/drm/tiny/simpledrm.c              | 179 ++++++++++++++----
 include/linux/platform_data/simplefb.h        |   1 +
 7 files changed, 274 insertions(+), 37 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/reserved-memory/framebuffer.yaml

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2.37.3