| To: | Ed Okerson <ed.okerson@gmail.com> |
|---|---|
| Subject: | Re: mmap KSEG1 |
| From: | David Daney <ddaney@caviumnetworks.com> |
| Date: | Fri, 04 Dec 2009 10:12:18 -0800 |
| Cc: | linux-mips@linux-mips.org |
| In-reply-to: | <83f0348b0912040952h40d4d151n79ca5fc33a830ee2@mail.gmail.com> |
| Original-recipient: | rfc822;linux-mips@linux-mips.org |
| References: | <83f0348b0912040952h40d4d151n79ca5fc33a830ee2@mail.gmail.com> |
| Sender: | linux-mips-bounce@linux-mips.org |
| User-agent: | Thunderbird 2.0.0.21 (X11/20090320) |
Ed Okerson wrote: Is it possible to mmap an address in KSEG1 so a user space app can read/write to an IO device uncached? It depends on your definition of 'possible'. The mips32/64 architecture specification has a 'C' field in the EntryLo register that controls cachability, so given an appropriate device driver it should be doable. Calling __ioremap() with the appropriate flags should allow you to set the 'C' bits. Depending on your requirements, you might be able to get by using /dev/mem and some 'sync' instructions, instead of establishing an uncached mapping. David Daney |
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