Hi!
> > During resume the IBM thinkpad with the cs46xx driver needs
> > to delay 700
> > milleseconds, so if the machine is booted up on battery power, then to
> > ensure that the delay is long enough, then a value of 3000
> > milleseconds is
> > must be programmed into the driver (3 seconds!). all the
> > mdelay and udelay
> > wait times are incorrect by the same factor, resulting in some serious
> > problems when attempting to wait specific delay times in
> > other parts of the
> > driver.
>
> Well yes this is a problem, but only when starting out with a low effective
> CPU freq and going high - the reverse is usually OK because longer than
> anticipated waits are OK.
>
> However, you can alleviate this problem by not using udelay (or mdelay) but
> using a kernel timer. I would think you should be doing this anyway (700ms
> is a LONG TIME) but this should also work regardless of effective CPU freq.
Going from 59usec to 19usec is probably as fatal as going from 10sec to 3sec.
> A grep of the kernel source shows cs46xx isn't even doing the biggest
> mdelay. I can understand the use of spinning on a calibrated loop for less
> than a clock tick, but I gotta think there are better ways for longer
> periods.
>
> I wonder if there is a way to modify mdelay to use a kernel timer if
> interval > 10msec? I am not familiar with this section of the kernel, but I
> do know that Microsoft's similar function KeStallExecutionProcessor is not
> recommended for more than 50 *micro*seconds.
You can't use kernel timer from within interrupts.
-- Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt, details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sat Mar 31 2001 - 21:00:19 EST