On Tue 13 Dec 11:45 PST 2016, Dwivedi, Avaneesh Kumar (avani) wrote:
> On 12/13/2016 11:39 PM, Bjorn Andersson wrote:
[..]
> >Either way, using the non-_relaxed version of writel() will be
> >equivalent to what you have now.
> Do you mean if writel is used , udelay() should be removed?
No, I mean that looping writel_relaxed() + wmb() is roughly
equivalent to writel(). So with the overall comment of you replacing
readl_relaxed() and writel_relaxed() with their plain readl/writel
counterparts takes care of the wmb().
> i understand
> writel will not return before register write operation is actually done.
> udelay() is to give enough time so that after writel , there is some time
> available to turn on mem peripheral and data array.
As far as I understand, wmb() will ensure that any cache coherent or
write-back buffered writes are committed before any subsequent writes.
But that this is not the same as the write has finished.
As far as I can see, the downstream code (msm-3.18) do:
for (i = 19; i >= 0; i--) {
val |= BIT(i);
writel_relaxed(val, MEM_PWR_CTL);
val |= readl_relaxed(MEM_PWR_CTL);
udelay(1);
}
I.e. for this particular version it actually does read back the value,
which will cause a wait for the write to be propagated. But I'm not sure
why this is the only version doing this.
Regards,
Bjorn
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