From 4394e96423444c1b37c8bb1ed0b1de8391dedafa Mon Sep 17 00:00:00 2001 From: Oleksandr Andrushchenko Date: Tue, 17 Apr 2018 10:40:12 +0300 Subject: drm/xen-front: Remove CMA support It turns out this was only needed to paper over a bug in the CMA helpers, which was addressed in commit 998fb1a0f478b83492220ff79583bf9ad538bdd8 Author: Liviu Dudau Date: Fri Nov 10 13:33:10 2017 +0000 drm: gem_cma_helper.c: Allow importing of contiguous scatterlists with nents > 1 Without this the following pipeline didn't work: domU: 1. xen-front allocates a non-contig buffer 2. creates grants out of it dom0: 3. converts the grants into a dma-buf. Since they're non-contig, the scatter-list is huge. 4. imports it into rcar-du, which requires dma-contig memory for scanout. -> On this given platform there's an IOMMU, so in theory this should work. But in practice this failed, because of the huge number of sg entries, even though the IOMMU driver mapped it all into a dma-contig range. With a guest-contig buffer allocated in step 1, this problem doesn't exist. But there's technically no reason to require guest-contig memory for xen buffer sharing using grants. Given all that, the xen-front cma support is not needed and should be removed. Signed-off-by: Oleksandr Andrushchenko Suggested-by: Daniel Vetter Acked-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20180417074012.21311-1-andr2000@gmail.com --- Documentation/gpu/xen-front.rst | 12 ------------ 1 file changed, 12 deletions(-) (limited to 'Documentation/gpu') diff --git a/Documentation/gpu/xen-front.rst b/Documentation/gpu/xen-front.rst index 009d942386c5..d988da7d1983 100644 --- a/Documentation/gpu/xen-front.rst +++ b/Documentation/gpu/xen-front.rst @@ -18,18 +18,6 @@ Buffers allocated by the frontend driver .. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h :doc: Buffers allocated by the frontend driver -With GEM CMA helpers -~~~~~~~~~~~~~~~~~~~~ - -.. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h - :doc: With GEM CMA helpers - -Without GEM CMA helpers -~~~~~~~~~~~~~~~~~~~~~~~ - -.. kernel-doc:: drivers/gpu/drm/xen/xen_drm_front.h - :doc: Without GEM CMA helpers - Buffers allocated by the backend -------------------------------- -- cgit