Hi Simon,

Simon Guinot [off-list ref] writes:

On Sat, Jun 01, 2013 at 07:26:54PM +0200, Arnaud Ebalard wrote:

quoted

Hi Simon and Guenter,

Simon Guinot [off-list ref] writes:

quoted

On Tue, May 28, 2013 at 12:03:14AM +0200, Arnaud Ebalard wrote:

quoted

Signed-off-by: Arnaud Ebalard <redacted>
---
 drivers/hwmon/Kconfig              |   10 +
 drivers/hwmon/Makefile             |    1 +
 drivers/hwmon/g762.c               | 1012 ++++++++++++++++++++++++++++++++++++
 include/linux/platform_data/g762.h |   54 ++
 4 files changed, 1077 insertions(+)
 create mode 100644 drivers/hwmon/g762.c
 create mode 100644 include/linux/platform_data/g762.h

Hi Arnaud,

After more tests on my 2Big Network v2 board, it appears that the fan
doesn't rotate when PWM mode (the preferred operating mode for this
board) is selected. Nevertheless, DC mode is usable (even if not ideal
given the hardware). After some investigations I noticed that an extra
initialization is needed to enable PWM mode on my board: the set_cnt
register must be set to 0 while the default value is 0xff. Is that
specific to my hardware ? Is PWM mode working on your ReadyNAS with
the default set_cnt value ?

First, thanks for testing this!

Regarding your problem, I first started by booting current version of my
driver on the Duo v2 w/o touching chip registers (only clock reference
value). This way, I inherit the values installed by (NETGEAR's) u-boot:

$ for k in fan* pwm* ; do echo -n "$k:" ; echo `cat $k `; done
fan1_alarm:0
fan1_div:2
fan1_fault:0
fan1_input:1807
fan1_target:1807
pwm1:221
pwm1_enable:2        /* closed-loop, i.e. config is done via set_cnt */
pwm1_mode:1          /* PWM mode */ 

Sorry, I realize that I have not been very accurate in my description of
the problem: The fan doesn't rotate when PWM _and_ open-loop control are
selected. On the 2Big2 board, 2 wires are used to drive the fan.

Then with pwm1_mode=1, pwm1_enable=1 and set_cnt=0xff (default value),
nothing happen whatever the value I write in pwm1.

After boot, with set_cnt and set_out untouched by me (set_cnt set to
0x5a by u-boot, i.e. 255-0x5a read on pwm1):

fan1_alarm:0
fan1_div:1
fan1_fault:0
fan1_input:1365
fan1_target:1365
pwm1:0                  /* set_out is 0 (considering fan1_target,
                           set_cnt is 0x5a)*/
pwm1_enable:2           /* closed-loop */
pwm1_mode:0             /* DC mode */

# echo 1 > pwm1_mode    /* PWM mode */       # fan rotates 
# echo 1 > pwm1_enable  /* open-loop */      # fan stops rotating

At that point we have:

fan1_alarm:0
fan1_div:1
fan1_fault:0
fan1_input:0
fan1_target:1365
pwm1:0                  /* set_out is 0, set_cnt is still 0x5a */
pwm1_enable:1
pwm1_mode:1

Then:

# echo 100 > pwm1                            # fan rotates

By testing, I have discovered that writing 0 into set_cnt allows to work
around the issue. I can do this by using the closed-loop control:
pwm1_mode=1, pwm1_enable=2 and pwm=255. Now, set_cnt worths 0 and if I
switch back to open-loop control, all works as expected.

Can you try open-loop control and PWM mode with your board ? I wonder if
this issue is specific to the 2Big2 hardware.

AFAICT, set_cnt has never been set to 0 in my test and PWM+open-loop
works as expected, i.e. just by setting a non-zero value in set_out.
Tell me if I missed something or if you want me to perform another
test.

Cheers,

a+