From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <39EBE0E7.B9313EEE@mvista.com> Date: Tue, 17 Oct 2000 01:17:27 -0400 From: Dan Malek MIME-Version: 1.0 To: paulus@linuxcare.com.au CC: Tilmann Bitterberg , Linux/PPC Development Subject: Re: HIGHMEM now working References: <14827.56089.260884.298273@argo.linuxcare.com.au> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Paul Mackerras wrote: > .... I personally think that the code in ioremap which > assigns virt = phys for phys >= ioremap_base should go away. Right, but that is just the most recent implementation for something we have to admit exists and we integrate into your HIGHMEM and other changes. We have to allow, somehow, mapping of board control registers or other resources that must be used prior to page tables or other VM initialization. Right now we map things in BATs or large TLB entries and then use the code above (or some other variation) to ensure the mapping sticks throughout the kernel lifetime. I don't think it has to be virt == phys (which is just convenient for assembly set up), but the mapping has to remain consistent even after the kernel VM has been initialized. The reason virt == phys is convenient is because we often access this space with and without the MMU enabled. We would have to add some code in the places this is done to further convert addresses, when right now we just write the functions without any MMU assumptions. -- Dan ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/