targets: add SATA support to ECPIX-5 - #773

Summary

• add optional Gen2 SATA support to the ECPIX-5 target with --with-sata
• instantiate the ECP5 PHY on DCU1 channel 0 and expose the LiteSATA read/write core to the BIOS
• generate the fixed 150MHz SATA reference clock from a dedicated PLL, independently of the configurable system clock
• correct the platform SATA resource to expose only the DCU differential RX/TX lanes

The default target remains unchanged when SATA is not enabled.

Hardware validation

Tested on an ECPIX-5 85F with a Toshiba DT01ACA100 HDD, using the target's default 75MHz system clock.

Build and load:

python3 litex_boards/targets/lambdaconcept_ecpix5.py \
    --with-sata \
    --build \
    --load

BIOS commands:

sata_init
sata_read 0
sata_read 1

Results:

• BIOS and SDRAM initialization completed successfully
• IDENTIFY reported TOSHIBA DT01ACA100, 1000GB
• Initialize SATA: OK
• DMA reads of LBA 0 and LBA 1 completed successfully
• returned data matched the continuous pattern previously written by the LiteSATA BIST
• BIOS reached SATA filesystem probing; mounting failed as expected since the test disk has no LiteX FAT boot volume

All routed clock domains pass timing:

• system: 95.47MHz achieved / 75.01MHz required
• SATA RX: 237.81MHz achieved / 150.01MHz required
• SATA TX: 251.51MHz achieved / 150.01MHz required

The target also elaborates successfully without --with-sata.

Dependency

This uses the ECP5 SATA PHY support from enjoy-digital/litesata#38. Its LiteICLink dependency, enjoy-digital/liteiclink#33, is already merged.