[L] Change in coreboot[main]: mb/lattepanda: Add support for LattePanda Mu

[Felix Singer (Code Review)]

Attention is currently required from: Felix Held, KunYi Chen, Martin L Roth, Nicholas Chin, Paul Menzel.

Felix Singer has posted comments on this change by KunYi Chen. ( https://review.coreboot.org/c/coreboot/+/83719?usp=email )

Change subject: mb/lattepanda: Add support for LattePanda Mu
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Patch Set 10:

(8 comments)

File src/mainboard/lattepanda/mu/devicetree.cb:

https://review.coreboot.org/c/coreboot/+/83719/comment/36526bed_340092ed?usp... :
PS10, Line 9: 	register "emmc_enable_hs400_mode" = "1"
Move this setting below the emmc device from the devicetree.

https://review.coreboot.org/c/coreboot/+/83719/comment/41c29903_4a9a05ef?usp... :
PS10, Line 11: 	register "sata_salp_support" = "0"
Settings are initialized with 0, please remove.

https://review.coreboot.org/c/coreboot/+/83719/comment/9b2bebef_a251d33c?usp... :
PS10, Line 38: 	register "serial_io_gspi_cs_mode" = "{
             : 		[PchSerialIoIndexGSPI0] = 0,
             : 		[PchSerialIoIndexGSPI1] = 0,
             : 		[PchSerialIoIndexGSPI2] = 0,
             : 		[PchSerialIoIndexGSPI3] = 0,
             : 	}"
             : 
             : 	register "serial_io_gspi_cs_state" = "{
             : 		[PchSerialIoIndexGSPI0] = 0,
             : 		[PchSerialIoIndexGSPI1] = 0,
             : 		[PchSerialIoIndexGSPI2] = 0,
             : 		[PchSerialIoIndexGSPI3] = 0,
             : 	}"
Settings are initialized with 0, please remove.

https://review.coreboot.org/c/coreboot/+/83719/comment/e9ec303a_2dd386ff?usp... :
PS10, Line 59: 	register "pch_hda_dsp_enable" = "1"
             : 	register "pch_hda_idisp_link_tmode" = "HDA_TMODE_8T"
             : 	register "pch_hda_idisp_link_frequency" = "HDA_LINKFREQ_96MHZ"
             : 	r
Move these settings below the hda device from the devicetree.

https://review.coreboot.org/c/coreboot/+/83719/comment/718b1d48_b172e597?usp... :
PS10, Line 103: 				[3] = USB2_PORT_EMPTY,
USB ports are disabled by default, remove.

https://review.coreboot.org/c/coreboot/+/83719/comment/d4d6de7c_e9605a10?usp... :
PS10, Line 110: 				[0] = USB3_PORT_EMPTY,
              : 		
Same here.

File src/mainboard/lattepanda/mu/spd/Makefile.mk:

https://review.coreboot.org/c/coreboot/+/83719/comment/e5bed233_9748a131?usp... :
PS10, Line 7: SPD_SOURCES += empty		# 0b004
This seems odd. Are these really needed?

File src/mainboard/lattepanda/mu/spd/empty.spd.hex:

PS10: 
Why is a zeroed SPD file needed?