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linux/drivers/w1/masters
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H. Nikolaus Schaller bedd8d6037 w1:omap_hdq: fix regression 
commit ecfaf0c42f upstream.

Commit e93762bbf6 ("w1: masters: omap_hdq: add support for 1-wire
mode") added a statement to clear the hdq_irqstatus flags in
hdq_read_byte().

If the hdq reading process is scheduled slowly or interrupts are
disabled for a while the hardware read activity might already be
finished on entry of hdq_read_byte().  And hdq_isr() already has set the
hdq_irqstatus to 0x6 (can be seen in debug mode) denoting that both, the
TXCOMPLETE and RXCOMPLETE interrupts occurred in parallel.

This means there is no need to wait and the hdq_read_byte() can just
read the byte from the hdq controller.

By resetting hdq_irqstatus to 0 the read process is forced to be always
waiting again (because the if statement always succeeds) but the
hardware will not issue another RXCOMPLETE interrupt.  This results in a
false timeout.

After such a situation the hdq bus hangs.

Link: http://lkml.kernel.org/r/b724765f87ad276a69625bc19806c8c8844c4590.1469513669.git.hns@goldelico.com
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2016-08-20 18:09:22 +02:00
..
ds1wm.c w1/masters: use pr_* instead of printk 2014-06-19 17:46:51 -07:00
ds2482.c w1: Drop owner assignment from i2c_driver 2015-08-05 13:48:20 -07:00
ds2490.c W1: ds2490: Increase timeout when waiting for status 2014-11-07 11:24:01 -08:00
Kconfig w1: mxc_w1: Enable driver compilation with COMPILE_TEST 2014-02-28 15:27:09 -08:00
Makefile w1: add 1-wire master driver for i.MX27 / i.MX31 2009-01-08 08:31:13 -08:00
matrox_w1.c Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2015-09-01 18:46:42 -07:00
mxc_w1.c w1: constify of_device_id array 2015-03-25 12:25:29 +01:00
omap_hdq.c w1:omap_hdq: fix regression 2016-08-20 18:09:22 +02:00
w1-gpio.c W1: w1-gpio - switch to using dev_pm_ops 2015-10-17 21:45:05 -07:00