On Wed, Oct 21, 2020 at 1:50 PM Aaron Durbin <[email protected]> wrote:
> > > On Wed, Oct 21, 2020 at 1:20 PM Tim Wawrzynczak via coreboot < > [email protected]> wrote: > >> Hi coreboot community, >> >> Currently there are 3 different "strapping" entries in the coreboot >> tables, and with the recent addition of fw_config ( >> https://review.coreboot.org/c/coreboot/+/41209), we would also like to >> add the 64-bit fw_config field (updated here >> https://review.coreboot.org/c/coreboot/+/45939) to the coreboot table as >> well. >> >> In this patch (https://review.coreboot.org/c/coreboot/+/46605), I am >> proposing to deprecate the 3 current "strapping" entries (board ID, ram >> code and SKU ID), and add them all to 1 entry, containing board ID, ram >> code, SKU ID as well as fw_config. This saves the overhead of parsing 4 >> different entries to obtain board configuration information. >> > > Not all of these entities are sourced through the same mechanism (gpios vs > cbi). As such any time you want to read one of those fields you'll be > unconditionally needing to obtain all of those while at the time the user > may only want one field. And then this can happen from multiple stages. > The patch I'm proposing doesn't change whether or not the functions `board_id()`, `ram_code()`, `sku_id()` are called or not, or their definition. It will, however, currently waste 12 bytes of space if none of the weak functions are overridden. However, if a board uses all 4 IDs, then this patch saves 20 bytes of space in the table on redundant tags/sizes in the records. I guess this is the tradeoff here. > I would say that since these things aren't all related to answering the > question someone may want to answer that we shouldn't go down this path. > Width of fields, e.g., could be different across platforms since not > everything is consistent. > I'm not sure I follow; board_id, ram_code and sku_id are all currently defined as 32 bits in coreboot/libpayload. > Would like to hear any thoughts on this, >> - Tim >> _______________________________________________ >> coreboot mailing list -- [email protected] >> To unsubscribe send an email to [email protected] >> >
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