Re: [PATCH][PPC32] Add setup_indirect_pci_nomap() routine

From: Mark A. Greer
Date: Mon Nov 08 2004 - 18:57:06 EST

Kumar Gala wrote:


Out of interest, why would we not want to ioremap the cfg addr/data registers?

- kumar

On Nov 8, 2004, at 4:56 PM, Mark A. Greer wrote:

This patch adds a routine that sets up indirect pci config space access
but doesn't ioremap the config space addr/data registers.

You do need them mapped, of course, but:

a) It so happens that on the marvell host bridges those regs are in the middle of a larger block that is already ioremapp'd.

b) [Warning: Long story...] To determine the type of bridge, the code has to access a pci cfg register on the bridge so access to those regs are necessary no matter what. However, some platforms that use the marvell bridges don't use one or both of the hoses. We've seen cases where if you try to access the pci bus that isn't wired properly, the bridge hangs so I can't always use pcibios_alloc_controller() to alloc the hose struct (or the pci infrastructure will try to scan the bus & hang the bridge). Instead, in the one routine that gets the bridge type, I temporarily use a hose struct alloc'd on the stack and call setup_indirect_pci[_nomap]() with it. Once I've read the bridge type, I no longer need that mapping but there is no "remove_indirect_pci()" routine to undo the previous setup. So, worst case, when a platform uses both hoses, those regs are mapped once when all the bridge's regs are mapped, a second time when the temporary mapping is used, and a third time when using a hose struct alloc'd by pcibios_alloc_controller(). I end up with two unused mappings.

With some work & ugly code, I could get rid of one extra mapping but not both, and making a "nomap" routine just seemed cleaner. There are probably other ppc platforms that could use this as well.


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