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authorH. Nikolaus Schaller <hns@goldelico.com>2016-08-02 14:07:12 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-08-20 18:09:22 +0200
commitbedd8d6037247002091d85d8abf4aa7e6c92ff24 (patch)
tree84bcf4df68fa21ceada080efede38ec15da1fbef
parent4a3e88a02e71cbc1dacfb958d8bffe0547d8fa2e (diff)
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w1:omap_hdq: fix regression
commit ecfaf0c42fc4306b5ec4bf6be01b66f8fe9a9733 upstream. Commit e93762bbf681 ("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>
-rw-r--r--drivers/w1/masters/omap_hdq.c2
1 files changed, 0 insertions, 2 deletions
diff --git a/drivers/w1/masters/omap_hdq.c b/drivers/w1/masters/omap_hdq.c
index 0e2f43bccf1f..0c427d6a12d1 100644
--- a/drivers/w1/masters/omap_hdq.c
+++ b/drivers/w1/masters/omap_hdq.c
@@ -390,8 +390,6 @@ static int hdq_read_byte(struct hdq_data *hdq_data, u8 *val)
goto out;
}
- hdq_data->hdq_irqstatus = 0;
-
if (!(hdq_data->hdq_irqstatus & OMAP_HDQ_INT_STATUS_RXCOMPLETE)) {
hdq_reg_merge(hdq_data, OMAP_HDQ_CTRL_STATUS,
OMAP_HDQ_CTRL_STATUS_DIR | OMAP_HDQ_CTRL_STATUS_GO,