[U-Boot] [RFC PATCH] usb: dwc2: handle bcm2835 phys->virt address translations

[Stephen Warren]

On 03/13/2015 12:13 AM, Stephen Warren wrote:
> BCM2835 bus addresses use the top 2 bits to determine whether peripherals
> use or bypass the GPU L1 and L2 cache. BCM2835-ARM-Peripherals.pdf states
> that:
> 
> 0: L1 & L2 cached
> 4: L2 cache coherent (non allocaing)
> 8: L2 cached only
> c: Direct uncached.
> 
> That document also states that "Software accessing RAM using the DMA
> engines must use bus addresses (base at 0xc0000000). However, this appears
> to be incorrect since it does not work in practice on the bcm2835
> (although it does on bcm2836). "usb start" causes some EABI function to
> call raise(8), presumably due to corrupted USB IN data (the converse is
> true on bcm2836; a value of 4 causes signals). However, I haven't
> investigated the cause.

I've confirmed that the raise(8) calls are due to corrupted USB IN data;
the maxpacketsize field in the device descriptor is getting corrupted to
0, which in turn surely causes division by zero when calculating the
number of packets in a transfer, for example.