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 > 762b1e88801357770889d013c5d20fe110d1f456. > > Signed-off-by: Paul Fertser <fercerpav@xxxxxxxxx> Patrick - any feedback ? Would it be possible to test this change with Quanta-q71l ? Or do you envision no problems ? Thanks, Guenter > --- > 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. */
