On Fri, Aug 9, 2019 at 8:16 AM Peter Zijlstra <pet...@infradead.org> wrote: > On Thu, Aug 08, 2019 at 12:07:28PM -0700, Linus Torvalds wrote: > > End result: a DRAM buffer can work, but is not "reliable". > > Particularly if you turn power on and off, data retention of DRAM is > > iffy. But it's possible, at least in theory. > > > > So I have a patch that implements a "stupid ring buffer" for thisa > > case, with absolutely zero data structures (because in the presense of > > DRAM corruption, all you can get is "hopefully only slightly garbled > > ASCII". > > Note that you can hook this into printk as a fake early serial device; > just have the serial device write to the DRAM buffer.
Yep. Amiga had debug=mem for years, to write kernel messages to Chip RAM, and retrieve them after a reboot. Cfr. amiga_console_driver and arch/m68k/tools/amiga/dmesg.c. BTW, with those old machines, it was not uncommon for DRAM retention time to be 30s or so. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds