Auf 11.03.2011 01:19, Jan Kiszka schrieb: > On 2011-03-10 23:10, Carl-Daniel Hailfinger wrote: > >> Auf 10.03.2011 22:55, Jordan Justen schrieb: >> >>> On Thu, Mar 10, 2011 at 13:37, Carl-Daniel Hailfinger >>> <c-d.hailfinger.devel.2...@gmx.net> wrote: >>> >>> >>>> Auf 10.03.2011 05:51, Jordan Justen schrieb: >>>> >>>> >>>>> I have documented a simple flash-like device which I think could be >>>>> useful for qemu/kvm in some cases. (Particularly for allowing >>>>> persistent UEFI non-volatile variables.) >>>>> >>>>> http://wiki.qemu.org/Features/System_Flash >>>>> >>>>> Let me know if you have any suggestions or concerns. >>>>> >>>>> >>>>> >>>> Is there any reason why you chose to invent an interface for the flash >>>> chip which is more complicated than the interface used by common flash >>>> chips out there? >>>> Maybe some EFI requirement? >>>> >>>> >>> This is a simpler version than the flash devices I'm used to dealing >>> with for x86/x86-64 UEFI systems. Can you suggest an alternative real >>> interface that is simpler? >>> >>> >> Pseudocode for the real interface most common on x86 before SPI came along: >> >> Write a page (256 bytes) or a few bytes: >> chip_writeb(0xAA, bios_base + 0x5555); >> chip_writeb(0x55, bios_base + 0x2AAA); >> chip_writeb(0xA0, bios_base + 0x5555); >> chip_writeb(databyte0, bios_base + addr); >> chip_writeb(databyte1, bios_base + addr + 1); >> chip_writeb(databyte2, bios_base + addr + 2); >> chip_writeb(databyte3, bios_base + addr + 3); >> ... up to 256 databytes. >> chip_readb(bios_base); >> The last chip_readb(bios_base) is repeated until the result does not >> change anymore. >> > Hmm, I may oversee some subtle difference, but this looks pretty much > like CFI to me (see hw/pflash_cfi02.c). >
I thought CFI also implements a way to retrieve device size/geometry with the Query (0x98) command, but that part is rarely implemented on x86 flash (I didn't see any yet). That said, the non-query commands are identical AFAICS. > At least it's an in-band interface, which is the better choice as we > currently only have a PIIX3 southbridge for x86, predating even FWHs. > Right, that pretty much kills the option of using SPI unless someone wants to emulate a flash translation controller (e.g. the ITE IT8716F Super I/O). Can be done, would work, but the IT8716F has some quirks (max 1 MB SPI flash chips) which make it a less desirable option for emulation. Regards, Carl-Daniel -- http://www.hailfinger.org/
