Dear Nico,
Am Sonntag, den 08.01.2017, 15:23 +0100 schrieb Nico Huber: > On 08.01.2017 14:38, Paul Menzel via coreboot wrote: > > looking at the coreboot CBMEM console messages board status repository, > > you’ll find a lot of truncated preram CBMEM console messages. > > > > Currently the buffer size is 0xc00 – 3 kB, right –, which is too small > > for quite some boards. The mainboard *Kabylake LPDDR3 RVP3* overrides > > it to 0xd00. > > > > So I am thinking about increasing it [1], but it’s of course not that > > simple, especially as I don’t understand all the implications. > > > > > Increasing this buffer reduces amount of available CAR stack, and > > > apparently DDR3 raminit already struggles with the amount of > > > cachelines available on fam10/15 > > This means a lower stack size (higher console buffer size) would result > in a stack overflow. In other words, a brick. One more question. How was the size 0xc00 chosen in the first place? > > My first question is, what other downsides are there of increasing the > > buffer size? I assume it’s unrelated to resulting usable RAM size, as > > RAM sizes nowadays are much, much bigger? So would one megabyte be > > reasonable/possible as a goal on boards supporting that? > > No, no other downsides beside bricking. > > > So if their is consensus that it should be increased, what would a way > > be forward? I assume, overriding it per mainboard is not so useful, as > > these messages are mostly from the chipset, so it should be chipset > > dependent? > > I would override it per chipset. Understood. I adapted the change set accordingly for the Intel 945 [1]. Testers are welcome. > But, for boards that implement the romstage main(), it has to be > tested for each board (a single declaration in the main() could > decide if the stack overflows or not). > > A better option would be to reduce the verbosity: Identify log messages > that are less useful (and could be hidden behind options like CONFIG_ > DEBUG_RAM_SETUP). Or something like disabling BIOS_SPEW messages if > CBMEM is the only console. > > > Should that option be moved there? Thanks, Paul > > [1] https://review.coreboot.org/18049/ > > "arch/x86: Increase preram CBMEM console buffer size"
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