From ecfaf0c42fc4306b5ec4bf6be01b66f8fe9a9733 Mon Sep 17 00:00:00 2001 From: "H. Nikolaus Schaller" Date: Tue, 2 Aug 2016 14:07:12 -0700 Subject: [PATCH] w1:omap_hdq: fix regression 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 Cc: Evgeniy Polyakov Cc: Greg Kroah-Hartman Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/w1/masters/omap_hdq.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/drivers/w1/masters/omap_hdq.c b/drivers/w1/masters/omap_hdq.c index a2eec97d5064..bb09de633939 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,