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 :
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
Am 20.07.2015 um 14:28 schrieb Guillaume Gardet: 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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