linux-kernel - [PATCH] mtd: rawnand: Fix unexpected timeouts in waitrdy

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Message-Id: <20191210150319.3125-1-devik@eaxlabs.cz>
Date:   Tue, 10 Dec 2019 16:03:18 +0100
From:   Martin Devera <devik@...labs.cz>
To:     linux-kernel@...r.kernel.org
Cc:     jan.pohanka@...z.cz,
        Christophe Kerello <christophe.kerello@...com>,
        Martin Devera <devik@...labs.cz>,
        Boris Brezillon <boris.brezillon@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org
Subject: [PATCH] mtd: rawnand: Fix unexpected timeouts in waitrdy

The used way to compute jiffies timeout brokes when
jiffie difference is 1. Simply add 1 - it has no other
side effects.
Fixes STM32MP1 FMC2 NAND controller which sometimes failed
exactly in this way.

Signed-off-by: Martin Devera <devik@...labs.cz>
---
 drivers/mtd/nand/raw/nand_base.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index d527e448ce19..beab3a775cc7 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -721,7 +721,11 @@ int nand_soft_waitrdy(struct nand_chip *chip, unsigned long timeout_ms)
 	if (ret)
 		return ret;
 
-	timeout_ms = jiffies + msecs_to_jiffies(timeout_ms);
+	/* +1 below is necessary because if we are now in the last fraction
+	 * of jiffy and msecs_to_jiffies is 1 then we will wait only that
+	 * small jiffy fraction - possibly leading to false timeout
+	 */
+	timeout_ms = jiffies + msecs_to_jiffies(timeout_ms) + 1;
 	do {
 		ret = nand_read_data_op(chip, &status, sizeof(status), true);
 		if (ret)
-- 
2.11.0