[U-Boot] Boot from USB support for Kirkwood SOC

[xiangfu]

Prafulla Wadaskar wrote:
> Dear Remy Bohmer
> 
> I am going to start "boot from USB Support" development for kirkwood.
what this "boot from USB Support" means?

I know "boot from nand", 
and I know that the Ingenic CPU, support "boot from USB". is the same meaning?

here is part of JZ4740 cpu data sheet [1]
--
3.7.3   BOOT
Jz4740 support 3 different boot sources depending on BOOT_SEL0 and BOOT_SEL1 pin values.
Table 3-29 lists them.
                             Table 3-29 Boot from 3 boot sources

BOOT_SEL1 BOOT_SEL0                Boot Source
    0         0     Boot from NOR flash at CS4
    0         1     Boot from USB device
    1         0     Boot from 512 page NAND flash at CS1
    1         1     Boot from 2k page NAND flash at CS1
--

[1] ftp://ftp.ingenic.cn/2soc/Jz4740_ds.pdf

> To sync with current USB framework in U-boot, and to reduce some rework at my side (since I am new to this driver).
> May you please provide some guidelines/howto this regard?
> 
> FYI below is details about Kirkwood USB controller:  
> 
> Kirkwood contains a Universal Serial Bus (USB 2.0) port that includes an embedded USB 2.0 PHY.
> The USB 2.0 interface contains a single dual-role controller that can act as a host or a peripheral
> controller (USB controller). A bridge connects the controller to the internal Mbus interface (USB
> bridge).
> Embedded USB 2.0 PHY features include:
> ?? 480 Mbps High Speed (HS)/ 12 Mbps Full Speed (FS) and 1.5 Mbps Low Speed (LS) serial data
> transmission rates
> ?? Synchronization/End-of-Packet (SYNC/EOP) generation and checking
> ?? Data and clock recovery from serial stream on the USB
> ?? Non Return to Zero Invert (NRZI) encoding/decoding with bit stuffing/unstuffing
> ?? Bit stuff error detections
> ?? Bit stuffing/unstuffing; bit stuff error detection
> ?? Holding registers to stage transmit and receive data
> ?? Supports USB 2.0 Test Modes
> ?? Ability to switch between FS and HS terminations/signaling
> ?? For more details, refer to the controller specification document USB-HS High-Speed
> Controller Core Reference.
> 
> Regards..
> Prafulla . .
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-- 
Best Regards
Xiangfu Liu

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