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patch "w1: mxc_w1: Fix timeout resolution problem leading to bus error" added to char-misc-testing

PATCH [email protected] 1 participant 1 message Oct 2, 2020

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Stable branch Arm i.MX and Layerscape W1 dallas's 1-wire bus
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This is a note to let you know that I've just added the patch titled

w1: mxc_w1: Fix timeout resolution problem leading to bus error

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From e1a26e13baf690444a254c4c4f088e1d059a942a Mon Sep 17 00:00:00 2001
From: Martin Fuzzey <[email protected]>
Date: Wed, 30 Sep 2020 10:36:46 +0200
Subject: 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 <[email protected]>
Signed-off-by Martin Fuzzey <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/w1/masters/mxc_w1.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)
drivers/w1/masters/mxc_w1.c +7 -7
index 1ca880e01476..090cbbf9e1e2 100644
@@ -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;
 }
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