[v2,00/10] drm: Add driver for PowerPC OF displays

Message

Thomas Zimmermann July 20, 2022, 2:27 p.m. UTC

(was: drm: Add driverof PowerPC OF displays)

PowerPC's Open Firmware offers a simple display buffer for graphics
output. Add ofdrm, a DRM driver for the device. As with the existing
simpledrm driver, the graphics hardware is pre-initialized by the
firmware. The driver only provides blitting, no actual DRM modesetting
is possible.

Version 2 of this patchset starts by cleaning up and refactoring
simpledrm, and moving some of the code in a helper library. These
functions are useful for ofdrm as well.

Patch 7 adds ofdrm, which has been significantly reworked since v1.
PCI is now optional and COMPILE_TEST is supported.

Patches 8 to 10 add support for color management. The code has been
taken from fbdev's offb. I have no hardware available for testing the
functionality. Qemu's stdvga apparently does not support gamma tables
in RGB modes. I verified that the color management code is executed
by running Gnome's night-mode settings, but the display's color tone
does not change.

Thomas Zimmermann (10):
  drm/simpledrm: Remove mem field from device structure
  drm/simpledrm: Inline device-init helpers
  drm/simpledrm: Remove pdev field from device structure
  drm/simpledrm: Compute framebuffer stride if not set
  drm/simpledrm: Convert to atomic helpers
  drm/simpledrm: Move some functionality into fwfb helper library
  drm/ofdrm: Add ofdrm for Open Firmware framebuffers
  drm/ofdrm: Add CRTC state
  drm/ofdrm: Add per-model device function
  drm/ofdrm: Support color management

 Documentation/gpu/drm-kms-helpers.rst |   12 +
 MAINTAINERS                           |    3 +
 drivers/gpu/drm/Kconfig               |    6 +
 drivers/gpu/drm/Makefile              |    3 +-
 drivers/gpu/drm/drm_fwfb_helper.c     |  301 ++++++
 drivers/gpu/drm/tiny/Kconfig          |   15 +
 drivers/gpu/drm/tiny/Makefile         |    1 +
 drivers/gpu/drm/tiny/ofdrm.c          | 1301 +++++++++++++++++++++++++
 drivers/gpu/drm/tiny/simpledrm.c      |  588 +++++------
 drivers/video/fbdev/Kconfig           |    1 +
 include/drm/drm_fwfb_helper.h         |   51 +
 11 files changed, 1949 insertions(+), 333 deletions(-)
 create mode 100644 drivers/gpu/drm/drm_fwfb_helper.c
 create mode 100644 drivers/gpu/drm/tiny/ofdrm.c
 create mode 100644 include/drm/drm_fwfb_helper.h

Comments

Michael Ellerman July 28, 2022, 11:13 a.m. UTC | #1

Thomas Zimmermann <[e-mail]> writes:
> (was: drm: Add driverof PowerPC OF displays)
>
> PowerPC's Open Firmware offers a simple display buffer for graphics
> output. Add ofdrm, a DRM driver for the device. As with the existing
> simpledrm driver, the graphics hardware is pre-initialized by the
> firmware. The driver only provides blitting, no actual DRM modesetting
> is possible.

Hi Thomas,

I tried to test this on a 32-bit ppc Mac Mini but didn't have much luck.
But I'm probably doing something wrong because I'm a graphics noob.

The machine normally uses CONFIG_DRM_RADEON, so I turned that off, and
turned DRM_OFDRM on.

When I boot I get boot messages but only one screen worth, the messages
don't scroll at all, which is unusual. But I'm not sure if that's
related to ofdrm or something else.

The machine does come up, I can login via SSH. Is there some way to
start X to exercise the driver from an SSH login?

cheers

Michal Suchánek July 28, 2022, 11:31 a.m. UTC | #2

Hello,

On Thu, Jul 28, 2022 at 09:13:59PM +1000, Michael Ellerman wrote:
> Thomas Zimmermann <[e-mail]> writes:
> > (was: drm: Add driverof PowerPC OF displays)
> >
> > PowerPC's Open Firmware offers a simple display buffer for graphics
> > output. Add ofdrm, a DRM driver for the device. As with the existing
> > simpledrm driver, the graphics hardware is pre-initialized by the
> > firmware. The driver only provides blitting, no actual DRM modesetting
> > is possible.
> 
> Hi Thomas,
> 
> I tried to test this on a 32-bit ppc Mac Mini but didn't have much luck.
> But I'm probably doing something wrong because I'm a graphics noob.
> 
> The machine normally uses CONFIG_DRM_RADEON, so I turned that off, and
> turned DRM_OFDRM on.
> 
> When I boot I get boot messages but only one screen worth, the messages
> don't scroll at all, which is unusual. But I'm not sure if that's
> related to ofdrm or something else.

A somewhat interesting datapoint might be how this works with offb.

> The machine does come up, I can login via SSH. Is there some way to
> start X to exercise the driver from an SSH login?

The startx script provided by distribution usually works.

It's basically a very convoluted way to do something like

X :0&
DISPLAY=:0 xterm&

Thanks

Michal