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drm/xe: Name and document Wa_14019789679

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Early in the development of Xe we identified an issue with SVG state
handling on DG2 and MTL (and later on Xe2 as well).  In
commit 72ac304769 ("drm/xe: Emit SVG state on RCS during driver load
on DG2 and MTL") and commit fb24b858a2 ("drm/xe/xe2: Update SVG state
handling") we implemented our own workaround to prevent SVG state from
leaking from context A to context B in cases where context B never
issues a specific state setting.

The hardware teams have now created official workaround Wa_14019789679
to cover this issue.  The workaround description only requires emitting
3DSTATE_MESH_CONTROL, since they believe that's the only SVG instruction
that would potentially remain unset by a context B, but still cause
notable issues if unwanted values were inherited from context A.
However since we already have a more extensive implementation that emits
the entire SVG state and prevents _any_ SVG state from unintentionally
leaking, we'll stick with our existing implementation just to be safe.

Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240812181042.2013508-2-matthew.d.roper@intel.com
This commit is contained in:
Matt Roper 2024-08-12 11:10:43 -07:00
parent d408d6f8cb
commit 1d734a3e5d
2 changed files with 27 additions and 10 deletions
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35
drivers/gpu/drm/xe/xe_lrc.c
View File

@ -5,6 +5,8 @@
#include "xe_lrc.h"
#include <generated/xe_wa_oob.h>
#include <linux/ascii85.h>
#include "instructions/xe_mi_commands.h"
@ -24,6 +26,7 @@
#include "xe_memirq.h"
#include "xe_sriov.h"
#include "xe_vm.h"
#include "xe_wa.h"
#define LRC_VALID BIT_ULL(0)
#define LRC_PRIVILEGE BIT_ULL(8)
@ -1581,19 +1584,31 @@ void xe_lrc_emit_hwe_state_instructions(struct xe_exec_queue *q, struct xe_bb *b
int state_table_size = 0;
/*
* At the moment we only need to emit non-register state for the RCS
* engine.
* Wa_14019789679
*
* If the driver doesn't explicitly emit the SVG instructions while
* setting up the default LRC, the context switch will write 0's
* (noops) into the LRC memory rather than the expected instruction
* headers. Application contexts start out as a copy of the default
* LRC, and if they also do not emit specific settings for some SVG
* state, then on context restore they'll unintentionally inherit
* whatever state setting the previous context had programmed into the
* hardware (i.e., the lack of a 3DSTATE_* instruction in the LRC will
* prevent the hardware from resetting that state back to any specific
* value).
*
* The official workaround only requires emitting 3DSTATE_MESH_CONTROL
* since that's a specific state setting that can easily cause GPU
* hangs if unintentionally inherited. However to be safe we'll
* continue to emit all of the SVG state since it's best not to leak
* any of the state between contexts, even if that leakage is harmless.
*/
if (q->hwe->class != XE_ENGINE_CLASS_RENDER)
return;
switch (GRAPHICS_VERx100(xe)) {
case 1255:
case 1270 ... 2004:
if (XE_WA(gt, 14019789679) && q->hwe->class == XE_ENGINE_CLASS_RENDER) {
state_table = xe_hpg_svg_state;
state_table_size = ARRAY_SIZE(xe_hpg_svg_state);
break;
default:
}
if (!state_table) {
xe_gt_dbg(gt, "No non-register state to emit on graphics ver %d.%02d\n",
GRAPHICS_VER(xe), GRAPHICS_VERx100(xe) % 100);
return;

2
drivers/gpu/drm/xe/xe_wa_oob.rules
View File

@ -35,3 +35,5 @@
GRAPHICS_VERSION(2001)
22019338487_display PLATFORM(LUNARLAKE)
16023588340 GRAPHICS_VERSION(2001)
14019789679 GRAPHICS_VERSION(1255)
GRAPHICS_VERSION_RANGE(1270, 2004)