i965/gen6/blorp: Set need_workaround_flush at top of blorp

Unconditionally set brw->need_workaround_flush at the top of gen6 blorp
state emission.

The art of emitting workaround flushes on Sandybridge is mysterious and
not fully understood. Ken and I believe that
intel_emit_post_sync_nonzero_flush() may be required when switching from
regular drawing to blorp.  This is an extra safety measure to prevent
undiscovered difficult-to-diagnose gpu hangs.

I verified that on ChromeOS, pre-patch, need_workaround_flush was not
set at the top of blorp, as Paul expected. To verify, I inserted the
following debug code at the top of gen6_blorp_exec(), restarted the ui,
and inspected the logs in /var/log/ui. The abort gets triggered so early
that the browser never appears on the display.

    static void
    gen6_blorp_exec(...)
    {
        if (!brw->need_workaround_flush) {
            fprintf(stderr, "chadv: %s:%d\n", __FILE__, __LINE__);
            abort();
        }
        ...
    }

CC: Kenneth Graunke <[email protected]>
CC: Stéphane Marchesin <[email protected]>
Reviewed-by: Paul Berry <[email protected]>
Signed-off-by: Chad Versace <[email protected]>

0 files changed, 0 insertions, 0 deletions