linux-kernel - [PATCH v1] net: Qcom WWAN control driver: fix the rx

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Date:   Tue, 20 Apr 2021 20:56:16 -0700
From:   Jarvis Jiang <jarvis.w.jiang@...il.com>
To:     davem@...emloft.net, kuba@...nel.org, loic.poulain@...aro.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jarvis Jiang <jarvis.w.jiang@...il.com>
Subject: [PATCH v1] net: Qcom WWAN control driver: fix the rx_budget was eaten incorrectly

mhi_wwan_rx_budget_dec() should check the value of mhiwwan->rx_budget
before the decrement, not the value after decrement.

When mhiwwan->rx_budget = 1, mhi_wwan_rx_budget_dec() will always return
false, which will cause the mhi_wwan_ctrl_refill_work() not to queue rx
buffers to transfer ring any more, and rx will be stuck.

This patch was tested with Ubuntu 20.04 X86_64 PC as host

Signed-off-by: Jarvis Jiang <jarvis.w.jiang@...il.com>
---
 drivers/net/wwan/mhi_wwan_ctrl.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c
index 11475ade4be5..721edf5a238f 100644
--- a/drivers/net/wwan/mhi_wwan_ctrl.c
+++ b/drivers/net/wwan/mhi_wwan_ctrl.c
@@ -56,12 +56,12 @@ static bool mhi_wwan_rx_budget_dec(struct mhi_wwan_dev *mhiwwan)
 
 	spin_lock(&mhiwwan->rx_lock);
 
-	if (mhiwwan->rx_budget)
-		mhiwwan->rx_budget--;
-
 	if (mhiwwan->rx_budget && test_bit(MHI_WWAN_RX_REFILL, &mhiwwan->flags))
 		ret = true;
 
+	if (mhiwwan->rx_budget)
+		mhiwwan->rx_budget--;
+
 	spin_unlock(&mhiwwan->rx_lock);
 
 	return ret;
-- 
2.25.1