[U-Boot] [PATCH v1 1/2] odroid: Update README with USB host information

[Suriyan Ramasami]

Add information wrt the USB host side of things for the Odroid-U2/U3 and the
Odroid-X/X2

Signed-off-by: Suriyan Ramasami <suriyan.r at gmail.com>
---

Changes in v1:
- Add USB host notes for the Odroid

 doc/README.odroid | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/doc/README.odroid b/doc/README.odroid
index 528bb95..0eaf3ff 100644
--- a/doc/README.odroid
+++ b/doc/README.odroid
@@ -141,3 +141,51 @@ And the boot sequence is:
 - boot_fit - if "Image.itb" exists
 - boot_zimg - if "zImage" exists
 - boot_uimg - if "uImage" exists
+
+11. USB host support
+====================
+The Odroid-X/X2 have the below schematics wrt USB:
+
+Exynos USB_HOST1 -> USB3503 HUB ----> LAN9514 USB HUB -----> LAN9514 Ethernet
+			|		|
+			|		+-------Host1---------> USB port
+			|		|
+			|		+-------Host2---------> USB port
+			|		|
+			|		+-------Host3---------> USB port
+			|		|
+			|		+-------Host4---------> USB port
+			|
+			+-------------------------------------> USB port
+			|
+			+-------------------------------------> USB port
+
+The Odroid-U2/U3 have the below schematics wrt USB:
+
+Exynos HSIC1 -----------------------------------------------> LAN9514 Ethernet
+
+Exynos HSIC2 -----> USB3503A HUB ---------------Host1---------> USB port
+			|
+			+-----------------------Host2---------> USB port
+			|
+			+-----------------------HOst3---------> USB port (U3)
+
+The HSICs are used in the case of the Odroid-Us and the USB Host in the SoC
+is used in the case of the Odroid-Xs.
+
+In drivers/usb/host/ehci-exynos.c, function names starting with exysno4412*
+have been added to initialize the HSICs and the PHYs.
+
+In board/samsung/odroid/odroid.c, function board_usb_init() adds code to
+initialize the USB3503 hub.
+The initializing of the USB3503 hub is as defined in the USB3503A spec sheet.
+Please refer to Figure 4.1 in the Datasheet.
+a) Set the INT_N (X30) low (Odroid-Us) or high (Odroid-Xs). This is so that the
+correct REFCLK frequency is selected. 24MHz for Odroid Us and 26MHz for Odroid
+Xs.
+b) Disconnect the HUB (Set HUB_CONNECT (X34) to 0)
+c) Reset the HUB (Set RESET_N (X35) to 0 and then to 1)
+d) HUB waits for REF_CLK (which we have set appropriately)
+e) Timeout waiting for HUB configuration stage
+f) Connect the HUB (Set HUB_CONNECT (X34) to 1)
+g) Power recycle the LAN9730 which is connected to BUCK8 (Odroid Us)
-- 
1.8.3.1