drm/xe/debugfs: add page-size allocation mode knob

Expose a debugfs control to override the page-size allocation mode used
for user BOs.

The interface allows switching between the default allocation policy,
forced 2M, forced 1G, and mixed allocation modes at runtime. This
provides a simple way to validate behavior and debug page-size-dependent
allocation flows.

The debugfs entry is built only when CONFIG_DRM_XE_DEBUG_PAGE_SIZE is
enabled.

v2
- update changelog to match mutex-based cur_index handling
- reset cur_index when switching to mixed mode (sashiko)

v3
- add CONFIG guard for page-size allocation debugfs support (Himal)
- create debugfs entry under CONFIG_DRM_XE_DEBUG_PAGE_SIZE

v4
- reorderd this patch with kconfig patch to ensure patch builds
- Gurding this debug knob for only discrete graphics

v5(Himal)
- Guard all page size calls with CONFIG_DRM_XE_DEBUG_PAGE_SIZE

v8(Himal)
- For read/show used READ_ONCE instead lock
- to match Reader used WRITE_ONCE under lock protection
- change modes to string format to read/writer for debugfs

v9(Himal)
- Add an OOB guard for mode in page_size_alloc_mode_show().
  This check makes the function display "unknown" if mode has been
  maliciously altered by KMD, preventing out-of-bounds access.
  Under normal operation, values set through debugfs are validated,
  so OOB values should not occur.
- simplify mode-to-string lookup using page_size_alloc_mode_names[]
- use sysfs_match_string() to parse page_size_alloc_mode writes

Signed-off-by: Nareshkumar Gollakoti <naresh.kumar.g@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patch.msgid.link/20260729121843.1255891-3-naresh.kumar.g@intel.com
Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>

0 files changed, 0 insertions, 0 deletions