linux-kernel - [PATCH] ata: pata_it821x: Replace mdelay with usleep_range in it821x_firmware

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Date:   Thu, 25 Jan 2018 18:32:59 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     b.zolnierkie@...sung.com, tj@...nel.org
Cc:     linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] ata: pata_it821x: Replace mdelay with usleep_range in it821x_firmware_command

After checking all possible call chains to it821x_firmware_command here,
my tool finds that it821x_firmware_command 
is never called in atomic context,
namely never in an interrupt handler or holding a spinlock.
And it821x_firmware_command calls kmalloc(GFP_KERNEL), 
so it proves again that it821x_firmware_command 
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/ata/pata_it821x.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/ata/pata_it821x.c b/drivers/ata/pata_it821x.c
index 7a21edf..8468b30 100644
--- a/drivers/ata/pata_it821x.c
+++ b/drivers/ata/pata_it821x.c
@@ -683,7 +683,7 @@ static u8 *it821x_firmware_command(struct ata_port *ap, u8 cmd, int len)
 			ioread16_rep(ap->ioaddr.data_addr, buf, len/2);
 			return (u8 *)buf;
 		}
-		mdelay(1);
+		usleep_range(500, 1000);
 	}
 	kfree(buf);
 	printk(KERN_ERR "it821x_firmware_command: timeout\n");
-- 
1.7.9.5