[U-Boot] USB ehci driver query

[Puneet Sharma]

Hello,

I am new to u-boot code. I am reading the usb host controller code for
root hub configuration. I have some queries regarding some code. If
anyone has got understanding about it pls explain it to me.

In usb.c the core calls the usb controller driver (ehci-hcd.c) by
issuing command GET_DESCRIPTOR to know the maximum packet size the
endpoint supports.

It than once again calls the driver by issuing command SET_ADDRESS to
give address 1 to root hub.

Than it issues command GET_DESCRIPTOR second time and this time creates
a queue head(QH) and associated queue transfer descriptors(qTD). The
code for
this is in function ehci_submit_async() (drivers/usb/host/ehci-hcd.c). I
am not getting the purpose of calling this function and what the usb
core is achieving by calling it.

If anyone can throw some light on it.

Regards
--
Puneet Sharma <puneet.sharma at moschip.com>


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