Add helpers for converting the pixel format of scanline. This used to be implemented for each format individually, but only the per-pixel code is really different among formats.
Patch 1 moves the per-pixel format helpers from drm_draw.c to an internal header. These functions have equivalents in the format-helper code. Just update the interface to make them exportable and add some comments. Patches 2 to 5 add generic line-conversion helpers. Each takes a scanline with pixels with a specific number of bits per pixel and converts it to a scanline with a specific number of bits per pixel. Conversion of each individual pixel is done by the provided per-pixel helper that was extracted from drm_draw.c. Patches 6 to 8 slightly optimize the line-conversion helpers by storing multiple pixels at once. With the current code, there are too many functions to make opimization feasible. But with the new helpers, there are only a few places to optimize to benefit all use cases. Here's a little benchmark for the common use case of watching a full-screen video under X. The tests measures the average time to display a single frame. It uses an XRGB8888 framebuffer for each frame, but displays it to an RGB565 scanout buffer, thus doing format conversion with the _32to16 helper. The test system is an Intel Core i5-3470 with an Intel HD2500 graphics card. The graphics driver is simpledrm at 1024x768 pixels. - 32-bit memcpy: 510 µs/frame - Current code: 1640 µs/frame - New (unoptimized): 1600 µs/frame - New (no 64-bit): 1580 µs/frame - New (optimized): 1470 µs/frame The first line shows the time to memcpy a single frame to video memory without format conversion. With conversion, the old and new code takes roughly 3 times as long. Both variants are comparable in performance. With 64-bit stores added, the new code is even 10% faster then the current one. (This is not to be considered a full performance test. The main objective is to see whether the new code is on par with the old code, which is the case.) Thomas Zimmermann (8): drm/format-helper: Move helpers for pixel conversion to header file drm/format-helper: Add generic conversion to 32-bit formats drm/format-helper: Add generic conversion to 24-bit formats drm/format-helper: Add generic conversion to 16-bit formats drm/format-helper: Add generic conversion to 8-bit formats drm/format-helper: Optimize 32-to-24-bpp conversion drm/format-helper: Optimize 32-to-16-bpp conversion drm/format-helper: Optimize 32-to-8-bpp conversion drivers/gpu/drm/drm_draw.c | 100 +------ drivers/gpu/drm/drm_format_helper.c | 378 ++++++++++++-------------- drivers/gpu/drm/drm_format_internal.h | 160 +++++++++++ 3 files changed, 339 insertions(+), 299 deletions(-) create mode 100644 drivers/gpu/drm/drm_format_internal.h -- 2.48.1
