Messages in this thread | | | Date | Mon, 29 Sep 2008 10:20:18 +0100 | From | Alan Cox <> | Subject | Re: [PATCH] pci: introduce users of ioremap_pcibar() |
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> 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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