Hi Søren,

2010/8/29 Søren Steen Christensen <lists@ssc-solutions.dk>
Hi Morten,

> Furthermore in kernel version 2.6.33 i had to change
arch/arm/mach-omap/usb-msub.c
> line 108 from "       musb_plat.power = board_data->power >> 1; " to
"musb_plat.power = board_data->power;"
> I am not sure if this is still necessary but this prohibited me from
specifying a supply of more than 250 mA
> removing the right shift allowed me to specify 500 mA.

First of all, I have to admit that I didn’t check the actual code, but are
you completely sure about the “>> 1” change?

In the USB-descriptor needed power is specified in steps of 2mA in the range
0-250 equal which equals 0-500mA in order to keep the field a 1-byte value.
I would expect that the right shift one actually tries to account for this
since you are entering real-world-mA in the board data specification?

After digging around in the source code, i know why i had to remove the >>1,
when i first did the change i did not notice that in arch/arm/plat-omap/usb.h 
the omap_musb_board_data structure has power defined as a u8 which combined with
right shift will give you maximum of 254 mA. Therefore instead of doing the change below i just removed
the right-shift and specified the power as mA/2  directly in board-overo.c.

I guess the correct change is to define the field "power" in the struct omap_musb_board_data in  arch/arm/plat-omap/usb.h as a u16 field instead, and leave the >> 1 which is correct according to the documentation in include/linux/usb/musb.h 

Am I correct about this?

 
Best regards and thanks
 Søren

---
SSC Solutions ApS - Denmark - www.ssc-solutions.dk



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Regards Morten Larsen