[PATCH] drm/xe/oa: Insert wmb/sfence before enabling OA

[Ashutosh Dixit]

We are occasionally seeing that OA Buffer register is not programmed (has
value 0) when OA is enabled. This means OA has been enabled before it has
been fully configured. Or, the register write enabling OA has overtaken
previous OA configuration register writes.

Therefore, insert a wmb/sfence to preserve OA register write ordering
before enabling OA.

v2: s/wmb()/xe_device_wmb()/

Fixes: e936f885f1e9 ("drm/xe/oa/uapi: Expose OA stream fd")
Reported-by: Guy Zadicario <guy.zadicario at intel.com>
Signed-off-by: Ashutosh Dixit <ashutosh.dixit at intel.com>
Cc: stable at vger.kernel.org
---
 drivers/gpu/drm/xe/xe_oa.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/xe/xe_oa.c b/drivers/gpu/drm/xe/xe_oa.c
index 63286ed8457fa..4fb7aae37a94f 100644
--- a/drivers/gpu/drm/xe/xe_oa.c
+++ b/drivers/gpu/drm/xe/xe_oa.c
@@ -440,6 +440,9 @@ static void xe_oa_enable(struct xe_oa_stream *stream)
 	val = __format_to_oactrl(format, regs->oa_ctrl_counter_select_mask) |
 		__oa_ccs_select(stream) | OAG_OACONTROL_OA_COUNTER_ENABLE;
 
+	/* Flush previous writes to HW before enabling OA */
+	xe_device_wmb(stream->oa->xe);
+
 	xe_mmio_write32(stream->gt, regs->oa_ctrl, val);
 }
 
-- 
2.41.0