linux-kernel - [PATCH] soc: mediatek: cmdq: fixup possible timeout issue

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Date:   Thu, 22 Oct 2020 17:41:53 +0800
From:   Houlong Wei <houlong.wei@...iatek.com>
To:     Matthias Brugger <matthias.bgg@...il.com>,
        Jassi Brar <jassisinghbrar@...il.com>
CC:     Daniel Kurtz <djkurtz@...omium.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <srv_heupstream@...iatek.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        CK HU <ck.hu@...iatek.com>,
        Bibby Hsieh <bibby.hsieh@...iatek.com>,
        Daoyuan Huang <daoyuan.huang@...iatek.com>,
        Dennis-YC Hsieh <dennis-yc.hsieh@...iatek.com>,
        Houlong Wei <houlong.wei@...iatek.com>,
        <ginny.chen@...iatek.com>, <yongqiang.niu@...iatek.com>
Subject: [PATCH] soc: mediatek: cmdq: fixup possible timeout issue

Fixes: 576f1b4bc802 ("soc: mediatek: Add Mediatek CMDQ helper")

There may be possible timeout issue when lots of cmdq packets are
flushed to the same cmdq client. The necessary modifications are as
below.
1.Adjust the timer timeout period as client->timeout_ms * client->pkt_cnt.
2.Optimize the time to start the timer.

Signed-off-by: Houlong Wei <houlong.wei@...iatek.com>
---
 drivers/soc/mediatek/mtk-cmdq-helper.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c
index dc644cfb6419..31142c193527 100644
--- a/drivers/soc/mediatek/mtk-cmdq-helper.c
+++ b/drivers/soc/mediatek/mtk-cmdq-helper.c
@@ -350,7 +350,8 @@ static void cmdq_pkt_flush_async_cb(struct cmdq_cb_data data)
 			del_timer(&client->timer);
 		else
 			mod_timer(&client->timer, jiffies +
-				  msecs_to_jiffies(client->timeout_ms));
+				  msecs_to_jiffies(client->timeout_ms *
+						   client->pkt_cnt));
 		spin_unlock_irqrestore(&client->lock, flags);
 	}
 
@@ -379,9 +380,7 @@ int cmdq_pkt_flush_async(struct cmdq_pkt *pkt, cmdq_async_flush_cb cb,
 
 	if (client->timeout_ms != CMDQ_NO_TIMEOUT) {
 		spin_lock_irqsave(&client->lock, flags);
-		if (client->pkt_cnt++ == 0)
-			mod_timer(&client->timer, jiffies +
-				  msecs_to_jiffies(client->timeout_ms));
+		client->pkt_cnt++;
 		spin_unlock_irqrestore(&client->lock, flags);
 	}
 
@@ -391,6 +390,21 @@ int cmdq_pkt_flush_async(struct cmdq_pkt *pkt, cmdq_async_flush_cb cb,
 	/* We can send next packet immediately, so just call txdone. */
 	mbox_client_txdone(client->chan, 0);
 
+	if (client->timeout_ms != CMDQ_NO_TIMEOUT) {
+		spin_lock_irqsave(&client->lock, flags);
+		/*
+		 * GCE HW maybe execute too quickly and the callback function
+		 * may be invoked earlier. If this happens, pkt_cnt is reduced
+		 * by 1 in cmdq_pkt_flush_async_cb(). The timer is set only if
+		 * pkt_cnt is greater than 0.
+		 */
+		if (client->pkt_cnt > 0)
+			mod_timer(&client->timer, jiffies +
+				  msecs_to_jiffies(client->timeout_ms *
+						   client->pkt_cnt));
+		spin_unlock_irqrestore(&client->lock, flags);
+	}
+
 	return 0;
 }
 EXPORT_SYMBOL(cmdq_pkt_flush_async);
-- 
2.18.0