[PATCH AUTOSEL 6.11 160/244] drm/xe: Name and document Wa_14019789679

Sasha Levin
2024-09-25T11:47:25Z

From: Matt Roper <matthew.d.roper@intel.com>

[ Upstream commit 1d734a3e5d6bb266f52eaf2b1400c5d3f1875a54 ]

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 72ac304769dd ("drm/xe: Emit SVG state on RCS during driver load
on DG2 and MTL") and commit fb24b858a20d ("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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/xe/xe_lrc.c | 35 +++++++++++++++++++++---------
drivers/gpu/drm/xe/xe_wa_oob.rules | 2 ++
2 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_lrc.c b/drivers/gpu/drm/xe/xe_lrc.c
index 58121821f0814..974a9cd8c3795 100644
--- a/drivers/gpu/drm/xe/xe_lrc.c
+++ b/drivers/gpu/drm/xe/xe_lrc.c
@@ -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;
diff --git a/drivers/gpu/drm/xe/xe_wa_oob.rules b/drivers/gpu/drm/xe/xe_wa_oob.rules
index 08f7336881e32..d4c33dbc14c7a 100644
--- a/drivers/gpu/drm/xe/xe_wa_oob.rules
+++ b/drivers/gpu/drm/xe/xe_wa_oob.rules
@@ -30,3 +30,5 @@
22019338487 MEDIA_VERSION(2000)
GRAPHICS_VERSION(2001)
16023588340 GRAPHICS_VERSION(2001)
+14019789679 GRAPHICS_VERSION(1255)
+ GRAPHICS_VERSION_RANGE(1270, 2004)
--
2.43.0