[SRU][A][PATCH 0/1] Fix for LP#1738334 - hibmc regression

Daniel Axtens daniel.axtens at canonical.com
Fri Dec 15 10:41:50 UTC 2017

[SRU Justification]

On Artful kernels, X fails to start and a kernel splat is printed.

This is because ea642c3216cb ("drm/ttm: add io_mem_pfn callback") is
incomplete: the hisilicon hibmc driver does not contain the callback
and so the kernel tries to execute code at NULL.

There is a discussion and potential fix at
The fix hasn't landed yet and it looks like they're going to
re-engineer the entire section instead.

Rather than wait for that and deal with the massive regression
potential, the fix I have picked to submit is very very minimal and
touches only hibmc.

[Regression Potential]
Minimal - fix only touches hibmc driver. Tested on D05 board.

Install patched kernel, try to start X. If it succeeds, the fix
works. If there's a kernel splat and X does not start, the fix does
not work.

HiSilicon would really like this fix in Artful in such time so that
when the next 16.04 point release ships in February, the HWE kernel
will work with Xorg.

Michal Srb (1):
  UBUNTU: SAUCE: drm: hibmc: Initialize the hibmc_bo_driver.io_mem_pfn

 drivers/gpu/drm/hisilicon/hibmc/hibmc_ttm.c | 1 +
 1 file changed, 1 insertion(+)


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