From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47DD53EF.9070302@domain.hid> Date: Sun, 16 Mar 2008 18:07:59 +0100 From: Philippe Gerum MIME-Version: 1.0 References: <47DD3BF9.2@domain.hid> <47DD3FB4.5080305@domain.hid> <47DD424A.7040006@domain.hid> <47DD47F0.5020003@domain.hid> <47DD4C70.2040208@domain.hid> <47DD4E1F.9050400@domain.hid> <47DD4FDA.8020105@domain.hid> In-Reply-To: <47DD4FDA.8020105@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: Philippe Gerum Subject: Re: [Xenomai-core] pgprot_noncached for io-remapping? Reply-To: rpm@xenomai.org List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Xenomai-core@domain.hid Jan Kiszka wrote: > Philippe Gerum wrote: >> Jan Kiszka wrote: >>> Philippe Gerum wrote: >>>> Jan Kiszka wrote: >>>>> Philippe Gerum wrote: >>>>>> Jan Kiszka wrote: >>>>>>> Hi, >>>>>>> >>>>>>> doesn't this patch [1] have some relevance for us as well? As we use >>>>>>> xnarch_remap_io_page_range also for non-IO memory, I'm hesitating to >>>>>>> suggest that we apply this unconditionally at xnarch level. Ideas welcome. >>>>>>> >>>>>> Yes, I think it makes a lot of sense on powerpc at least, since doing so will >>>>>> set the PAGE_GUARDED bit as well, and we obviously want to avoid any >>>>>> out-of-order access of I/O memory. >>>>>> >>>>>> (I don't see the reason to force the VM_RESERVED and VM_IO on the vma though, >>>>>> since remap_pfn_range will do it anyway.) >>>>> No, I was talking about cases where we may pass kmalloc'ed memory to >>>>> xnarch_remap_io_page_range. In that case, caching and out-of-order >>>>> access may be desired for performance reasons. >>>>> >>>> xnarch_remap_io_page_range is intended for I/O memory only, some assumptions are >>>> made on this. rtdm_mmap_buffer() should be fixed; it would be much better to >>>> define another internal interface at xnarch level to specifically perform >>>> kmalloc mapping. >>> Yeah, probably. But I think the issue is not just limited to RTDM. The >>> xnheap can be kmalloc-hosted as well. >>> >> This one is used with DMA memory. What I would suggest, is something like this: >> >> --- ksrc/skins/rtdm/drvlib.c (revision 3590) >> +++ ksrc/skins/rtdm/drvlib.c (working copy) >> @@ -1738,9 +1738,12 @@ >> } >> return 0; >> } else >> -#endif /* CONFIG_MMU */ >> return xnarch_remap_io_page_range(vma, maddr, paddr, >> size, PAGE_SHARED); >> +#else >> + return xnarch_remap_kmem_page_range(vma, maddr, paddr, >> + size, PAGE_SHARED); >> +#endif /* CONFIG_MMU */ >> } >> >> static struct file_operations rtdm_mmap_fops = { >> >> >> I.e. split the cases where MMU is absent from the one where MMU is there but we >> come from rtdm_iomap_to_user. > > Makes no sense to me yet. With CONFIG_MMU we have 3 cases, not just two, > no? We have to use mmap_data->src_paddr to tell kmem_page apart from > io_page. That's what the patch I sent right after this one does. > > And we do not need io_page at all in the !CONFIG_MMU case? > MMU-less platforms may still control caching at page range level (e.g. Blackfin via CPLBs), so we have to be flexible as well. > Jan > -- Philippe.