From: Kenneth Graunke Date: Sun, 18 Jan 2015 07:21:15 +0000 (-0800) Subject: i965: Work around mysterious Gen4 GPU hangs with minimal state changes. X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=c4fd0c9052dd391d6f2e9bb8e6da209dfc7ef35b;p=mesa.git i965: Work around mysterious Gen4 GPU hangs with minimal state changes. Gen4 hardware appears to GPU hang frequently when using Chromium, and also when running 'glmark2 -b ideas'. Most of the error states contain 3DPRIMITIVE commands in quick succession, with very few state packets between them - usually VERTEX_BUFFERS/ELEMENTS and CONSTANT_BUFFER. I trimmed an apitrace of the glmark2 hang down to two draw calls with a glUniformMatrix4fv call between the two. Either draw by itself works fine, but together, they hang the GPU. Removing the glUniform call makes the hangs disappear. In the hardware state, this translates to removing the CONSTANT_BUFFER packet between the two 3DPRIMITIVE packets. Flushing before emitting CONSTANT_BUFFER packets also appears to make the hangs disappear. I observed a slowdown in glxgears by doing it all the time, so I've chosen to only do it when BRW_NEW_BATCH and BRW_NEW_PSP are unset (i.e. we haven't done a CS_URB_STATE change or already flushed the whole pipeline). I'd much rather understand the problem, but at this point, I don't see how we'd ever be able to track it down further. We have no real tools, and the hardware people moved on years ago. I've analyzed 20+ error states and read every scrap of documentation I could find. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80568 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85367 Signed-off-by: Kenneth Graunke Acked-by: Matt Turner Cc: "10.4 10.3" --- diff --git a/src/mesa/drivers/dri/i965/brw_curbe.c b/src/mesa/drivers/dri/i965/brw_curbe.c index c3d3b9d2131..d0ec8595c45 100644 --- a/src/mesa/drivers/dri/i965/brw_curbe.c +++ b/src/mesa/drivers/dri/i965/brw_curbe.c @@ -285,6 +285,19 @@ brw_upload_constant_buffer(struct brw_context *brw) */ emit: + /* Work around mysterious 965 hangs that appear to happen if you do + * two 3DPRIMITIVEs with only a CONSTANT_BUFFER inbetween. If we + * haven't already flushed for some other reason, explicitly do so. + * + * We've found no documented reason why this should be necessary. + */ + if (brw->gen == 4 && !brw->is_g4x && + (brw->state.dirty.brw & (BRW_NEW_BATCH | BRW_NEW_PSP)) == 0) { + BEGIN_BATCH(1); + OUT_BATCH(MI_FLUSH); + ADVANCE_BATCH(); + } + /* BRW_NEW_URB_FENCE: From the gen4 PRM, volume 1, section 3.9.8 * (CONSTANT_BUFFER (CURBE Load)): *