On Tue, May 19, 2020 at 11:44:17AM +0200, Geert Uytterhoeven wrote: > Hi Łukasz > > Thanks for your report! > > On Tue, May 19, 2020 at 10:54 AM Lukasz Stelmach <l.stelmach@xxxxxxxxxxx> wrote: > > It was <2020-04-29 śro 10:21>, when Geert Uytterhoeven wrote: > > > Currently, the start address of physical memory is obtained by masking > > > the program counter with a fixed mask of 0xf8000000. This mask value > > > was chosen as a balance between the requirements of different platforms. > > > However, this does require that the start address of physical memory is > > > a multiple of 128 MiB, precluding booting Linux on platforms where this > > > requirement is not fulfilled. > > > > > > Fix this limitation by obtaining the start address from the DTB instead, > > > if available (either explicitly passed, or appended to the kernel). > > > Fall back to the traditional method when needed. > > > > > > This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM > > > on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), > > > i.e. not at a multiple of 128 MiB. > > > > > > Suggested-by: Nicolas Pitre <nico@xxxxxxxxxxx> > > > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > > > Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxxx> > > > Reviewed-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> > > > Tested-by: Dmitry Osipenko <digetx@xxxxxxxxx> > > > --- > > > > [...] > > > > Apparently reading physical memory layout from DTB breaks crashdump > > kernels. A crashdump kernel is loaded into a region of memory, that is > > reserved in the original (i.e. to be crashed) kernel. The reserved > > region is large enough for the crashdump kernel to run completely inside > > it and don't modify anything outside it, just read and dump the remains > > of the crashed kernel. Using the information from DTB makes the > > decompressor place the kernel outside of the dedicated region. > > > > The log below shows that a zImage and DTB are loaded at 0x18eb8000 and > > 0x193f6000 (physical). The kernel is expected to run at 0x18008000, but > > it is decompressed to 0x00008000 (see r4 reported before jumping from > > within __enter_kernel). If I were to suggest something, there need to be > > one more bit of information passed in the DTB telling the decompressor > > to use the old masking technique to determain kernel address. It would > > be set in the DTB loaded along with the crashdump kernel. > > Shouldn't the DTB passed to the crashkernel describe which region of > memory is to be used instead? Definitely not. The crashkernel needs to know where the RAM in the machine is, so that it can create a coredump of the crashed kernel. > Describing "to use the old masking technique" sounds a bit hackish to me. > I guess it cannot just restrict the /memory node to the reserved region, > as the crashkernel needs to be able to dump the remains of the crashed > kernel, which lie outside this region. Correct. > However, something under /chosen should work. Yet another sticky plaster... -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC for 0.8m (est. 1762m) line in suburbia: sync at 13.1Mbps down 424kbps up
