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Date: Wed, 1 Mar 2017 18:06:30 +0530
From: Aishwarya Pant <aishpant@gmail.com>
To: Lidza Louina <lidza.louina@gmail.com>,
	Mark Hounschell <markh@compro.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: outreachy-kernel@googlegroups.com
Subject: [PATCH v4] staging: dgnc: replace usleep_range with udelay
Message-ID: <20170301123630.GA3820@aishwarya>
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User-Agent: Mutt/1.5.24 (2015-08-30)

udelay is impelmented using a busy-wait loop and consumes CPU cycles
while usleep_range is implemented using interrupts.cls_flush_uart_write()
is called after a channel lock is acquired i.e. an atomic context.
Hence delay in this method should use udelay instead of usleep_range.

Signed-off-by: Aishwarya Pant <aishpant@gmail.com>

---
Changes in v4:
	- Fix comment format
	- Edit line comment in code
Changes in v3:
	- Add a comment in code udelay to ignore checkpatch warning
Changes in v2:
    	- Edit commit message to explain why udelay should be used

 drivers/staging/dgnc/dgnc_cls.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/dgnc/dgnc_cls.c b/drivers/staging/dgnc/dgnc_cls.c
index 28a3e16..3112c25 100644
--- a/drivers/staging/dgnc/dgnc_cls.c
+++ b/drivers/staging/dgnc/dgnc_cls.c
@@ -609,7 +609,9 @@ static void cls_flush_uart_write(struct channel_t *ch)
 
 	writeb((UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_XMIT),
 	       &ch->ch_cls_uart->isr_fcr);
-	usleep_range(10, 20);
+
+	/* Must use *delay family functions in atomic context */
+	udelay(10);
 
 	ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
 }
-- 
2.7.4