Change in flashrom[master]: ite_ec: Implement support for flashing ITE ECs found on TUXEDO laptops

[Michael Niewöhner (Code Review)]

Attention is currently required from: Nico Huber, Michał Żygowski, Paul Menzel.
Michael Niewöhner has posted comments on this change. ( https://review.coreboot.org/c/flashrom/+/55715 )

Change subject: ite_ec: Implement support for flashing ITE ECs found on TUXEDO laptops
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Patch Set 13:

(1 comment)

File ite_ec.c:

https://review.coreboot.org/c/flashrom/+/55715/comment/a9260ea9_773456f9 
PS13, Line 78: struct ite_string {
L140CU signatures:
eflash: A5 A5 A5 A5  A5 A5 A5 94  85 12 5A 5A  AA 00 55 55
spi:    A5 A5 A5 A5  A5 A5 A5 95  85 12 5A 5A  AA 7F 55 55

Some details on the signature:

Mirroring is done from external SPI flash to eFlash.
There's a "mirror once" or "always mirror" feature, controlled by the FW.

A5 A5 A5 A5  A5 A5 TT UU  85 12 VV WW  AA XX YY ZZ

TT:   bit 0: eSPI/LPC mode
        0: eSPI -> TT=A4
        1: LPC  -> TT=A5

UU:   bit 7: PWM blinking during mirroring
        0: enable
        1: disable
      bit 6: use internal clock until external crystal is ready
        0: disable
        1: enable (only valid when bit 4 = 0)
      bit 5: FSPI mirror function
        0: enable (XX must be set)
        1: disable (XX must be AA)
      bit 4: 32.768 kHz source
        0: external crystal
        1: internal OSC, crystal-free mode
      bit 3: ec code base mode
        0: implicit - YYZZ must be 5555
        1: explicit
      bit 2: CRC-16 check after mirror
        0: enable, VVWW must be CRC-16 of mirrored region
        1: disable
      bit 1: must be 0
      bit 0: PWM selector for blinking
        0: PWM0
        1: PWM1

XX:   mirror size if mirror enabled: XX = (size - 1); e.g. 128k = 7F
      must be a multiple of 4k
      else AA

VVWW: CRC-16 of mirrored region, if CRC enabled; else 5A 5A

YYZZ: 5555 if implicit format used or signature on e-flash (code base is
      the start of the 4k block, where the signature is located)
      else if explicit format: YYZZ = BASE[23:12]