[PATCH 1/3] parisc: led: Reduce CPU overhead for disk & lan LED computation

[deller@kernel.org]

From: Helge Deller <deller@gmx.de>

Older PA-RISC machines have LEDs which show the disk- and LAN-activity.
The computation is done in software and takes quite some time, e.g. on a
J6500 this may take up to 60% time of one CPU if the machine is loaded
via network traffic.

Since most people don't care about the LEDs, start with LEDs disabled and
just show a CPU heartbeat LED. The disk and LAN LEDs can be turned on
manually via /proc/pdc/led.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org>
---
 drivers/parisc/led.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/parisc/led.c b/drivers/parisc/led.c
index 8bdc5e043831..765f19608f60 100644
--- a/drivers/parisc/led.c
+++ b/drivers/parisc/led.c
@@ -56,8 +56,8 @@
 static int led_type __read_mostly = -1;
 static unsigned char lastleds;	/* LED state from most recent update */
 static unsigned int led_heartbeat __read_mostly = 1;
-static unsigned int led_diskio    __read_mostly = 1;
-static unsigned int led_lanrxtx   __read_mostly = 1;
+static unsigned int led_diskio    __read_mostly;
+static unsigned int led_lanrxtx   __read_mostly;
 static char lcd_text[32]          __read_mostly;
 static char lcd_text_default[32]  __read_mostly;
 static int  lcd_no_led_support    __read_mostly = 0; /* KittyHawk doesn't support LED on its LCD */
@@ -589,6 +589,9 @@ int __init register_led_driver(int model, unsigned long cmd_reg, unsigned long d
 		return 1;
 	}
 	
+	pr_info("LED: Enable disk and LAN activity LEDs "
+		"via /proc/pdc/led\n");
+
 	/* mark the LCD/LED driver now as initialized and 
 	 * register to the reboot notifier chain */
 	initialized++;
-- 
2.41.0