https://bugs.freedesktop.org/show_bug.cgi?id=97477

Bug ID: 97477 Summary: i915g: gl_FragCoord is always (0.0, max_y) Product: Mesa Version: git Hardware: Other OS: All Status: NEW Severity: normal Priority: medium Component: Drivers/Gallium/i915g Assignee: dri-devel@lists.freedesktop.org Reporter: nicholasbishop@gmail.com QA Contact: dri-devel@lists.freedesktop.org

Created attachment 126029 --> https://bugs.freedesktop.org/attachment.cgi?id=126029&action=edit Patch: Handle I915_SEMANTIC_POS when setting texCoords for gl_FragCoord

On Intel Pineview M hardware, the i915 gallium driver doesn't output the correct gl_FragCoord. It seems to always have an X coord of 0.0 and a Y coord of the window's height in pixels, e.g. 600.0f or such.

I believe this is a regression caused in part by commit afa035031ff9e0c07a2297d864e46c76f7bfff58 (https://lists.freedesktop.org/archives/mesa-commit/2016-January/061181.html)

The old behavior used output zero, while the new behavior uses actual zeroes. In the case of gl_FragCoord output zero happened to be the correct one.

I've attached a patch that seems to fix the issue for me. I ran the piglit "quick" tests and observed 17 new tests passing, and one regression. I suspect the regression is unimportant since it involves derivatives that aren't implemented for this driver anyway:

"fs-dfdy-accuracy" test failed ... in i915_fpc_translate.c: case TGSI_OPCODE_DDY: /* XXX We just output 0 here */ debug_printf("Punting DDX/DDX\n");