From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <39D66E4D.4364FC8B@mvista.com> Date: Sat, 30 Sep 2000 15:50:53 -0700 From: Frank Rowand Reply-To: frowand@mvista.com MIME-Version: 1.0 To: paulus@linuxcare.com.au CC: frowand@mvista.com, Dan Malek , Geert Uytterhoeven , Linux/PPC Development Subject: Re: __ioremap_at() in 2.4.0-test9-pre2 References: <19340822040932.8760@mailhost.mipsys.com> <14803.57550.118150.759977@argo.linuxcare.com.au> <39D41AA2.C586D738@mvista.com> <14804.7238.688771.238444@argo.linuxcare.com.au> <39D4E85F.926CFD5B@mvista.com> <14805.17492.766815.388301@argo.linuxcare.com.au> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-dev@lists.linuxppc.org List-Id: Paul Mackerras wrote: > > Frank Rowand writes: > > > Paul Mackerras wrote: > [snip] > > > Because we'll make it the same value for all ports. Anybody got any > > > objections to 0xff000000? > > > Yes. It is equivalently mapped on the PPC 405 at 0xe8000000. > > But that's a physical address, not necessarily a virtual address, > right? I was talking about virtual address 0xff000000. Any > particular reason why you have to have virtual == physical? (If there > is, my response will probably be "fix it". :-) If the answer ends up "fix it", that's fine. Dan Malek has been providing me lots of review of the code I've been doing for the 405, helping me to learn the Linux PowerPC way of doing things so I have lots of practice at fixing things. The address 0xe8000000 is both the physical and the virtual address ("equivalently mapped"). I can move the virtual address to 0xff000000 (kernel people can do anything, right?). This raises a question about equivalent mapping though. Everything above ioremap_base is equivalently mapped by ioremap(). In 2.4.0-test2 ioremap_base is initialized in MMU_init(): 0xe8000000 #ifdef CONFIG_IBM405 0xfffff000 #ifdef CONFIG_POWER4 0xf0000000 _MACH_prep 0xf8000000 _MACH_Pmac 0xe0000000 _MACH_8260 0xf8000000 everything else Is it wise to hardcode a virtual address of 0xff000000 to a specific object? If that is done, then an ioremap of physical address 0xff000000 will also have the same virtual address. What am I missing? So to answer your question, I arbitrarilly chose 0xe8000000 as ioremap_base because it seemed within reason, given other existing values. I can move ioremap_base to lots of other places if I need to. > > Paul. > > -- > Paul Mackerras, Senior Open Source Researcher, Linuxcare, Inc. > +61 2 6262 8990 tel, +61 2 6262 8991 fax > paulus@linuxcare.com.au, http://www.linuxcare.com.au/ > Linuxcare. Support for the revolution. Thanks, Frank -- Frank Rowand MontaVista Software, Inc ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/