[PATCH 4.14 071/125] w1: mxc_w1: Fix timeout resolution problem leading to bus error

Greg Kroah-Hartman
2020-11-03T21:16:20Z

From: Martin Fuzzey <martin.fuzzey@flowbird.group>

commit c9723750a699c3bd465493ac2be8992b72ccb105 upstream.

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@vger.kernel.org>
Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group>
Link: https://lore.kernel.org/r/1601455030-6607-1-git-send-email-martin.fuzzey@flowbird.group
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/w1/masters/mxc_w1.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

--- a/drivers/w1/masters/mxc_w1.c
+++ b/drivers/w1/masters/mxc_w1.c
@@ -15,7 +15,7 @@
#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/platform_device.h>

@@ -47,12 +47,12 @@ 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);

@@ -62,7 +62,7 @@ static u8 mxc_w1_ds2_reset_bus(void *dat
/* 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;
}
@@ -75,12 +75,12 @@ static u8 mxc_w1_ds2_reset_bus(void *dat
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);

@@ -90,7 +90,7 @@ static u8 mxc_w1_ds2_touch_bit(void *dat
/* 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;
}