linux-kernel - [PATCH] w1: mxc_w1: Fix timeout resolution problem leading to bus error

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Date:   Wed, 30 Sep 2020 10:36:46 +0200
From:   Martin Fuzzey <martin.fuzzey@...wbird.group>
To:     Evgeniy Polyakov <zbr@...emap.net>
Cc:     Alexander Shiyan <shc_work@...l.ru>,
        stable <stable@...r.kernel.org>, linux-kernel@...r.kernel.org
Subject: [PATCH] w1: mxc_w1: Fix timeout resolution problem leading to bus error

On my platform (i.MX53) bus access sometimes fails with
	w1_search: max_slave_count 64 reached, will continue next search.

The reason is the use of jiffies to implement a 200us timeout in
mxc_w1_ds2_touch_bit().
On some platforms the jiffies timer resolution is insufficient for this.

Fix by replacing jiffies by ktime_get().

For consistency apply the same change to the other use of jiffies in
mxc_w1_ds2_reset_bus().

Fixes: f80b2581a706 ("w1: mxc_w1: Optimize mxc_w1_ds2_touch_bit()")
Cc: stable <stable@...r.kernel.org>

Signed-off-by: Martin Fuzzey <martin.fuzzey@...wbird.group>
---
 drivers/w1/masters/mxc_w1.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/w1/masters/mxc_w1.c b/drivers/w1/masters/mxc_w1.c
index 1ca880e..090cbbf 100644
--- a/drivers/w1/masters/mxc_w1.c
+++ b/drivers/w1/masters/mxc_w1.c
@@ -7,7 +7,7 @@
 #include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/io.h>
-#include <linux/jiffies.h>
+#include <linux/ktime.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 #include <linux/platform_device.h>
@@ -40,12 +40,12 @@ struct mxc_w1_device {
 static u8 mxc_w1_ds2_reset_bus(void *data)
 {
 	struct mxc_w1_device *dev = data;
-	unsigned long timeout;
+	ktime_t timeout;
 
 	writeb(MXC_W1_CONTROL_RPP, dev->regs + MXC_W1_CONTROL);
 
 	/* Wait for reset sequence 511+512us, use 1500us for sure */
-	timeout = jiffies + usecs_to_jiffies(1500);
+	timeout = ktime_add_us(ktime_get(), 1500);
 
 	udelay(511 + 512);
 
@@ -55,7 +55,7 @@ static u8 mxc_w1_ds2_reset_bus(void *data)
 		/* PST bit is valid after the RPP bit is self-cleared */
 		if (!(ctrl & MXC_W1_CONTROL_RPP))
 			return !(ctrl & MXC_W1_CONTROL_PST);
-	} while (time_is_after_jiffies(timeout));
+	} while (ktime_before(ktime_get(), timeout));
 
 	return 1;
 }
@@ -68,12 +68,12 @@ static u8 mxc_w1_ds2_reset_bus(void *data)
 static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
 {
 	struct mxc_w1_device *dev = data;
-	unsigned long timeout;
+	ktime_t timeout;
 
 	writeb(MXC_W1_CONTROL_WR(bit), dev->regs + MXC_W1_CONTROL);
 
 	/* Wait for read/write bit (60us, Max 120us), use 200us for sure */
-	timeout = jiffies + usecs_to_jiffies(200);
+	timeout = ktime_add_us(ktime_get(), 200);
 
 	udelay(60);
 
@@ -83,7 +83,7 @@ static u8 mxc_w1_ds2_touch_bit(void *data, u8 bit)
 		/* RDST bit is valid after the WR1/RD bit is self-cleared */
 		if (!(ctrl & MXC_W1_CONTROL_WR(bit)))
 			return !!(ctrl & MXC_W1_CONTROL_RDST);
-	} while (time_is_after_jiffies(timeout));
+	} while (ktime_before(ktime_get(), timeout));
 
 	return 0;
 }
-- 
1.9.1