linux-kernel - [PATCH v2 4/7] tty: xuartps: Don't write IRQ disable register to enable interrupts

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Date:	Mon, 10 Mar 2014 14:40:07 -0700
From:	Soren Brinkmann <soren.brinkmann@...inx.com>
To:	Russell King <linux@....linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	Michal Simek <michal.simek@...inx.com>,
	Peter Crosthwaite <peter.crosthwaite@...inx.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-serial@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Rob Landley <rob@...dley.net>,
	Grant Likely <grant.likely@...aro.org>,
	devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
	Soren Brinkmann <soren.brinkmann@...inx.com>
Subject: [PATCH v2 4/7] tty: xuartps: Don't write IRQ disable register to enable interrupts

A comment states, that, according to the data sheet, to enable
interrupts the disable register should be written, but the enable
register could be left untouched. And it suspsects a HW bug requiring
to write both.
Reviewing the data sheet, these statements seem wrong. Just as one would
expect. Writing to the enable/disable register enables/disables
interrupts.
Hence the misleading comment and needless write to the disable register
are removed from the enable sequence.

Signed-off-by: Soren Brinkmann <soren.brinkmann@...inx.com>
---
I added a few lines to comment the change and altered the summary line.
In case this causes issues it should show up a little easier as a
candidate to revert.

	Sören
---
 drivers/tty/serial/xilinx_uartps.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index a4bd6242e72d..a39c2d290902 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1082,11 +1082,7 @@ static void xuartps_console_write(struct console *co, const char *s,
 
 	xuartps_writel(ctrl, XUARTPS_CR_OFFSET);
 
-	/* restore interrupt state, it seems like there may be a h/w bug
-	 * in that the interrupt enable register should not need to be
-	 * written based on the data sheet
-	 */
-	xuartps_writel(~imr, XUARTPS_IDR_OFFSET);
+	/* restore interrupt state */
 	xuartps_writel(imr, XUARTPS_IER_OFFSET);
 
 	if (locked)
-- 
1.9.0.1.g4196000

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