Re: [RFC][PATCH] bcmai: introduce AI driver
From: Arend van Spriel
Date: Thu Apr 07 2011 - 04:58:54 EST
On Thu, 07 Apr 2011 09:54:46 +0200, Michael BÃsch <mb@xxxxxxxxx> wrote:
Ahh, so while talking about 4 windows, I guess you counted fixes
windows as well. That would be right, matching my knowledge.
When asking question about amount of cores we may want to use
simultaneously I didn't think about ChipCommon or PCIe. The real
problem would be to support for example two 802.11 cores and one
ethernet core at the same time. That gives us 3 cores while we have
only 2 sliding windows.
Would that really be a problem? Think of it. This combination
will only be available on embedded devices. But do we have windows
on embedded devices? I guess not. If AXI is similar to SSB, the MMIO
of all cores will always be mapped. So accesses can be done
without switch or lock.
Agree. For embedded systems there is no need to switch cores. Each core
register space and wrapper register space is mapped. In the brcm80211 we
have the concept of fast versus slow host interface. The criteria for fast
host interface is based on following expression:
fast_host_bus = (host_bus_coretype == PCIE_CORE_ID) ||
((host_bus_coretype == PCI_CORE_ID) && (host_bus_corerev >= 13))
If this is true, chipcommon and pci/pcie registers are accessed without
sliding the window using the fixed offsets RafaÅ mentioned earlier. The
BAR0 window size is 16KB.
I do really think that engineers at broadcom are clever enough
to design a hardware that does not require expensive window sliding
all the time while operating.
If a bigger window is clever enough ;-)
Gr. AvS
--
"The most merciful thing in the world, I think, is the inability of the
human
mind to correlate all its contents." - "The Call of Cthulhu"
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