On Fri Jun 25 around 14:01:51 EST 2010 Kyle Moffett wrote: > Oops... put the old linuxppc list on the CC, sorry! > > On Thu, Jun 24, 2010 at 23:45, Kyle Moffett <kyle at moffetthome.net> wrote: > > Hello, > > > > I've got a new P2020 (32bit mpc85xx family) board I'm working on a > > port for that includes 2 NOR flashes (128MB each) and a removable > > SO-RDIMM of 2GB or 4GB. Unfortunately when I configure both flashes > > in the device-tree off my elbc, Linux is completely unable to access > > the second one because it attempts to ioremap() the entire virtual > > address space of both FLASH chips. > > > > Even with only one flash chip enabled, there's a bit of a noticeable > > performance degradation because the mapping consumes almost all of my > > available vmalloc space and forces bounce-buffering for all my > > HIGHMEM. > > > > It looks like the "of-flash" driver currently requires that the whole > > chip be mapped in the kernel at once. I would much rather have a 50% > > performance penalty on flash accesses (which are already very slow) > > and regain most of the vmap space. > > > > So the question is, is there a way to convince the MTD layer to > > iomap() only what it needs to access to do reads and writes? If not, > > what changes would need to be made to MTD and/or "of-flash" to create > > such functionality? > > > > Cheers, > > Kyle Moffett > >
I believe the MTD layer would be happy, but it is beyond the scope of the physmap_of driver. A look at drivers/mtd/maps/pcmciamtd.c shows the concept of paging in a section of flash, although it has the advantage of hardware to move the window instead of calling ioremap or swapping translations. Another example is drivers/mtd/maps/pci.c, also with hardware assist. milton _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
