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

[Ashutosh Dixit]

We are occasionally seeing warnings such as "OAG Buffer register is not
programmed (has value 0). Register offset db08".  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>
---
 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