On Mon, Sep 09, 2024 at 08:40:30AM +0200, Thomas Zimmermann wrote:

Hi

Am 09.09.24 um 07:15 schrieb Yan Zhao:

quoted

Use ioremap_wc() instead of ioremap() to map framebuffer during driver
probing phase.

Using ioremap() results in a VA being mapped with PAT=UC-. Additionally,
on x86 architectures, ioremap() invokes memtype_reserve() to reserve the
memory type as UC- for the physical range. This reservation can cause
subsequent calls to ioremap_wc() to fail to map the VA with PAT=WC to the
same physical range for framebuffre in ttm_kmap_iter_linear_io_init().
Consequently, the operation drm_gem_vram_bo_driver_move() ->
ttm_bo_move_memcpy() -> ttm_move_memcpy() becomes significantly slow on
platforms where UC memory access is slow.

I've noticed this too and pushed a major update that replaces the entire
memory management. [1]

The patch is still welcome, I think, but you may want to rebase onto the
latest drm-misc-next branch. [2]

Best regards
Thomas

[1] https://patchwork.freedesktop.org/series/138086/
[2] https://gitlab.freedesktop.org/drm/misc/kernel/-/tree/drm-misc-next

Thanks!

The updated version is at
https://lore.kernel.org/all/20240909131643.28915-1-yan.y.zhao@intel.com (local)