linux-kernel - [PATCH] mtd: nand: diskonchip: Replace mdelay with usleep_range in doc

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Date:   Wed, 11 Apr 2018 10:57:57 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     boris.brezillon@...e-electrons.com, richard@....at,
        dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, cyrille.pitchen@...ev4u.fr
Cc:     linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] mtd: nand: diskonchip: Replace mdelay with usleep_range in doc_probe

doc_probe() is never called in atomic context.

doc_probe() is only called by init_nanddoc(), which is only set as 
a parameter of module_init().
This function is not called in atomic context.

Despite never getting called from atomic context, doc_probe()
calls mdelay() to busily wait.
This is not necessary and can be replaced with usleep_range() to
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.
And I also manually check it.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/mtd/nand/diskonchip.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/diskonchip.c b/drivers/mtd/nand/diskonchip.c
index c3aa53c..2679bc4 100644
--- a/drivers/mtd/nand/diskonchip.c
+++ b/drivers/mtd/nand/diskonchip.c
@@ -1482,12 +1482,12 @@ static int __init doc_probe(unsigned long physadr)
 		WriteDOC(tmp, virtadr, Mplus_DOCControl);
 		WriteDOC(~tmp, virtadr, Mplus_CtrlConfirm);
 
-		mdelay(1);
+		usleep_range(1000, 2000);
 		/* Enable the Millennium Plus ASIC */
 		tmp = DOC_MODE_NORMAL | DOC_MODE_MDWREN | DOC_MODE_RST_LAT | DOC_MODE_BDECT;
 		WriteDOC(tmp, virtadr, Mplus_DOCControl);
 		WriteDOC(~tmp, virtadr, Mplus_CtrlConfirm);
-		mdelay(1);
+		usleep_range(1000, 2000);
 
 		ChipID = ReadDOC(virtadr, ChipID);
 
-- 
1.9.1