[PATCH] hwmon: (aspeed-pwm-tacho) increase fan tach period (again)
linux at roeck-us.net
Thu Jul 21 13:49:46 AEST 2022
On Thu, Jul 14, 2022 at 05:23:44PM +0300, Paul Fertser wrote:
> The old value allows measuring fan speeds down to about 970 RPM and
> gives timeout for anything less than that. It is problematic because it
> can also be used as an indicator for fan failure or absence.
> Despite having read the relevant section of "ASPEED AST2500/AST2520 A2
> Datasheet – V1.7" multiple times I wasn't able to figure out what
> exactly "fan tach period" and "fan tach falling point of period" mean
> (both are set by the driver from the constant this patch is amending).
> Experimentation with a Tioga Pass OCP board (AST2500 BMC) showed that
> value of 0x0108 gives time outs for speeds below 1500 RPM and the value
> offered by the patch is good for at least 750 RPM (the fans can't spin
> any slower so the lower bound is unknown). Measuring with the fans
> spinning takes about 30 ms, sometimes down to 18 ms, so about the same
> as with the previous value.
> This constant was last changed in
> Signed-off-by: Paul Fertser <fercerpav at gmail.com>
I did not get any further feedback, so:
Applied to linux-next.
> drivers/hwmon/aspeed-pwm-tacho.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/drivers/hwmon/aspeed-pwm-tacho.c b/drivers/hwmon/aspeed-pwm-tacho.c
> index 3cb88d6fbec0..d11f674e3dc3 100644
> --- a/drivers/hwmon/aspeed-pwm-tacho.c
> +++ b/drivers/hwmon/aspeed-pwm-tacho.c
> @@ -159,7 +159,7 @@
> * 11: reserved.
> #define M_TACH_MODE 0x02 /* 10b */
> -#define M_TACH_UNIT 0x0210
> +#define M_TACH_UNIT 0x0420
> #define INIT_FAN_CTRL 0xFF
> /* How long we sleep in us while waiting for an RPM result. */
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