From 8ab44bd49b5554275e7bb24c17527d887b238e76 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 5698ca336c21 ("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 a2eec97d50649..bb09de6339392 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, -- 2.39.5