Michael Buesch wrote:
On Tuesday 27 June 2006 04:27, Larry Finger wrote:
Jeff Garzik wrote:
John W. Linville wrote:
+ assert(bcm->mac_suspended >= 0);
+ if (bcm->mac_suspended == 0) {
+ bcm43xx_power_saving_ctl_bits(bcm, -1, 1);
+ bcm43xx_write32(bcm, BCM43xx_MMIO_STATUS_BITFIELD,
+ bcm43xx_read32(bcm,
BCM43xx_MMIO_STATUS_BITFIELD)
+ & ~BCM43xx_SBF_MAC_ENABLED);
+ bcm43xx_read32(bcm, BCM43xx_MMIO_GEN_IRQ_REASON); /* dummy
read */
+ for (i = 100000; i; i--) {
+ tmp = bcm43xx_read32(bcm, BCM43xx_MMIO_GEN_IRQ_REASON);
+ if (tmp & BCM43xx_IRQ_READY)
+ goto out;
+ udelay(10);
+ }
+ printkl(KERN_ERR PFX "MAC suspend failed\n");
}
NAK this super-long delay... should be done in a workqueue, looks like?
ACK everything else.
That delay was set to try to accommodate my interface when it refused to suspend the MAC, which
resulted in transmit errors. That problem has since been cured by reworking the periodic work
handlers - thus such a long delay should not be needed. The original spec from the clean-room group
was a delay loop of 1000. I'm currently testing that value now. If it passes the test, would a for
(i=1000; i; i--) be acceptable?
Short: Don't touch it. Fullstop.
Long: The delay will _never_ be exhausted. Actually the for-counter
is only there to not lock up the machine, if there is a Bug in the
driver. (__much__ easier debugging).
The loop will only iterate a few times, typically.
Actually, _if_ we want to change something, we should do this:
for (i = 1000000; i; i--) {
...
udelay(1);
}
(max loop multiplied by 10, delay value divided by 10).
This will shorten the whole delay by a few usecs (up to 10).
I will send a patch for this, if it is desired.
But lowering the loop counter value is NACKed by me,
because it simply does not make sense.
My overriding concern was that this type of loop spins the CPU at 100%
until the hardware condition is satisfied, which starves all other
kernel work on that CPU, and is very unfriendly to power consumption
(though I believe monitor/mwait/cpu_relax helps on x86).
Overall, bcm43xx is _really really bad_ about this sort of thing. Just
grepping for udelay in bcm43xx_radio.c shows some of the worst
offenders. bcm43xx_radio_init2060() and bcm43xx_radio_selectchannel()
both look like candidates for using msleep() rather than udelay().
Jeff
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