On Fri, Mar 09, 2012 at 03:49:57PM +0530, KARTHIK SEKURU wrote:
Hi,
I am new to linux-kernel and am using kernel 3.1.6 and working on arm-SemiHosting(through USB) drivers.
We are using SemiHosting to exchange/transfer data from the arm-board to the PC.
What is SemiHosting?
Board details –
Using ARM926e-js processor with 128MB SDRAM., Clock-33Mhz
SDRAM Size = 128M
CONFIG_PAGE_OFFSET = 0xc0000000 CONFIG_PHYS_OFFSET= 0x80000000 Kernel Lowmem = 32M including 8M for initramfs (starting from 24M to 32M). HighMEM is not configured. Vmalloc_start = end address of LowMem (i.e 0xC200000) VMALLOC_END = Vmalloc_start + 64M = 0xC6000000
The SemiHosting(USB) drivers have read(); write(); seek(); functionalities along with an InitUSB function that initializes the semihosting USB hardware unit on the arm board.
Is this a USB host controller, or a device controller? Do you have a pointer to where this code is somewhere so we can see what it does?
We are using kernel ioremap() function for accessing the USB register set, which is remaped to malloc section.
Are these are the USB controller's register set for a host device, or a "gadget"?
Functionality in semihosting init (InitUSB) function –
1. We send header command to hostPC via USB DMA operation by setting few USB registers.
Setting them where?
USB DMA takes the start address of the header and it’s size and these two params (addr, size) are set into corresponding USB registers.
The USB transfer is enabled by setting USB_EN register to appropriate value.
2.After header transfer acknowledgement from hostPC should be received.
As acknowledgement , hostPC should set INTC_USB register, we poll for this register and once this is set we are done with the initialisation.
I wanted to test if the InitUSB function is working as expected. So I called this function in the start_kernel(after Console_Init()).
As this function is just setting few registers and polling for few registers., I io_remaped this register set in the InitUSB function..
But the INTC_USB register that is set by the hostPC as acknowledgement is not getting set and the code is never coming out of the while loop.
Now, I wanted to know if the place from where the InitUSB() function is called is the culprit and due to it if I am not receiving acknowledgement from the PC.
As mentioned I am calling the Init_USB function in the start_kernel(after Console_Init()).
I think a pointer to the code would be the easiest for us to understand exactly what is going on here. Also, USB specific questions are best asked on the linux-usb@vger.kernel.org mailing list, have you tried there? thanks, greg k-h