RPM calculation from tachometer value does not depend on PPR.
Also, do not report negative RPM values.
Signed-off-by: Chris D Schimp <silverchris@gmail.com>
[guenter.roeck@ericsson.com: do not report negative RPM values] Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com> Acked-by: Roland Stigge <stigge@antcom.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>