On 07/23/15 14:43, Andreas Färber wrote:
Am 23.07.2015 um 14:22 schrieb Guillaume Gardet:
Le 23/07/2015 14:16, Andreas Färber a écrit :
Am 20.07.2015 um 14:28 schrieb Guillaume Gardet:
Le 19/07/2015 18:15, Misha Komarovskiy a écrit :
Also lcd screen stays black after kernel start, probably some drm
module still missing.
Upstream kernel is broken. :(
How did you test? Actually there's a known issue that the Exynos IOMMU
support breaks graphics on the Chromebooks because they enable a
framebuffer early in bootloaders, before Linux initializes the IOMMU.
Since some other platforms do need the IOMMU, I fear that we're going to
need a new kernel flavor... :/ Not sure if that can be scripted as lpae
minus certain options?
You mean that if we disable IOMMU in kernel, graphics are working fine?
Hopefully yes. I did not test the latest kernel. It used to be that way
~3 months ago in linux-next.git (cf. linux-samsung-soc) and I doubt it's
improved.
CONFIG_DRM_EXYNOS_IOMMU is enabled. Should we disable it for chromebooks?
Yes. But at some point that got auto-selected, so it may be necessary to
disable IOMMU or the corresponding Exynos sub-option completely.
Maybe some config options compiled as module (which?) and blacklisted
for chromebooks could be ok?
Maybe. Someone with a Chromebook needs to sit down and try. :)
Hrm, rather than disable it one way or another manually, couldn't we
just blacklist it inside the kernel? I doubt that we can load iommu as
module...
Alex
Regards,
Andreas
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