linux-kernel - [PATCH] dmaengine: idxd: Clear Event Log head in idxd upon completion of the Enable Device command

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Date: Fri,  9 Feb 2024 11:18:51 -0800
From: Fenghua Yu <fenghua.yu@...el.com>
To: "Vinod Koul" <vkoul@...nel.org>,
	"Dave Jiang" <dave.jiang@...el.com>
Cc: dmaengine@...r.kernel.org,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Lingyan Guo <lingyan.guo@...el.com>
Subject: [PATCH] dmaengine: idxd: Clear Event Log head in idxd upon completion of the Enable Device command

If Event Log is supported, upon completion of the Enable Device command,
the Event Log head in the variable idxd->evl->head should be cleared to
match the state of the EVLSTATUS register. But the variable is not reset
currently, leading mismatch of the variable and the register state.
The mismatch causes incorrect processing of Event Log entries.

Fix the issue by clearing the variable after completion of the command.

Fixes: 2f431ba908d2 ("dmaengine: idxd: add interrupt handling for event log")
Tested-by: Lingyan Guo <lingyan.guo@...el.com>
Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 drivers/dma/idxd/device.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index ecfdf4a8f1f8..7c9fb9b3e110 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -546,6 +546,14 @@ int idxd_device_enable(struct idxd_device *idxd)
 		return -ENXIO;
 	}
 
+	/*
+	 * If Event Log is supported, Event Log Status register was
+	 * cleared after the Enable Device command. Clear Event Log
+	 * head value that is stored in idxd to match the register state.
+	 */
+	if (idxd->evl)
+		idxd->evl->head = 0;
+
 	idxd->state = IDXD_DEV_ENABLED;
 	return 0;
 }
-- 
2.37.1