linux-kernel - [PATCH] atm: idt77252: Replace mdelay with usleep_range in idt77252

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Date:   Fri, 26 Jan 2018 11:42:18 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     3chas3@...il.com
Cc:     linux-atm-general@...ts.sourceforge.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] atm: idt77252: Replace mdelay with usleep_range in idt77252_preset

After checking all possible call chains to idt77252_preset() here,
my tool finds that idt77252_preset() is never called in atomic context,
namely never in an interrupt handler or holding a spinlock.
And idt77252_preset() calls deinit_card, which calls free_irq (can sleep),
so it indicates that idt77252_preset() can call functions which can sleep.
Thus mdelay can be replaced with usleep_range to avoid busy wait.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/atm/idt77252.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/atm/idt77252.c b/drivers/atm/idt77252.c
index 0277f36..cea4bf2 100644
--- a/drivers/atm/idt77252.c
+++ b/drivers/atm/idt77252.c
@@ -3563,7 +3563,7 @@ static int idt77252_preset(struct idt77252_dev *card)

 	/* Software reset */
 	writel(SAR_CFG_SWRST, SAR_REG_CFG);
-	mdelay(1);
+	usleep_range(500, 1000);
 	writel(0, SAR_REG_CFG);

 	IPRINTK("%s: Software resetted.\n", card->name);
-- 
1.7.9.5