Re: [PATCH] pci: introduce users of ioremap_pcibar()
From: Alan Cox
Date: Mon Sep 29 2008 - 05:20:49 EST
> FTR, I like this interface better since most drivers use ioremap() instead
> of ioremap_nocache(). They generally should be using the latter.
And pci_iomap is cleaner still. Plus pcim_iomap does resource tracking so
all the masses of special case error code/cleanup can get cut down.
> Is there any easy way to tell if the device driver should be using
> uncached mappings vs cacheable mappings?
> (Just from looking at the source code)
There isn't one.
> For storage/networking/audio cards I'm comfortable with the generalization
> that they all should use uncacheable mappings (I'm sure there are some
> exceptions.) I'm not with video devices.
There are exceptions - I2O for example and there are other cards that use
write merging when possible beyond video. Also btw vidoe depends on the
chip - if you cache/write merge the framebuffer on a Voodoo 1/2 card you
must be in 24/32bit video modes for example.
Generally though PCI = controlled by hardware = uncached
Alan
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