Thanks guys.
The msleep solution looks good, but if my device does its work in 1
micro or nano second then it seems a tad too long to sleep. Here is
what I ended up using -
{
.
unsigned long long delta = (cpu/khz/HZ)*2;
unsigned long long _start = 0;
unsigned long long _cur = 0;
.
timeout = rdstcll(start) + delta ;
while (1) {
if (_cur < timeout) {
rdstcll(_cur);
} else {
flag_error()
}
}
-Asim
On 3/7/09, Greg KH <greg@xxxxxxxxx> wrote:
> On Fri, Mar 06, 2009 at 12:17:37PM -0600, Asim wrote:
>> I need it for a device. The device performs some operation in a loop
>> but I cannot wait in that loop forever, so I need to wait for the
>> maximum time I can (2 clock ticks) before giving up on the device.
>> Interrupts may be disabled so I cannot use jiffies. Any simple
>> solution would be appreciated.
>
> Do what is done in lots of places in the kernel, something like the
> following from drivers/usb/host/pci-quirks.c:
>
> /* if boot firmware now owns EHCI, spin till
> * it hands it over.
> */
> msec = 1000;
> while ((cap & EHCI_USBLEGSUP_BIOS) && (msec > 0)) {
> tried_handoff = 1;
> msleep(10);
> msec -= 10;
> pci_read_config_dword(pdev, offset, &cap);
> }
>
> Don't think in "clock ticks" but rather in "real" units of time, like
> portions of seconds. That way your code will work properly when a
> "clock tick" changes over time, becoming faster or slower, as they
> always do.
>
> Hope this helps,
>
> greg k-h
>
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