Correct Place of calling a driver initialization function.

[KARTHIK SEKURU]

 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?
SemiHosting is a way to tranfer/exchange data b/w arm-board and the PC.
We have an application USBConsole.exe running on the windows machine that
controls/interfaces with the USB uint on the
arm board.

> 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?
It is neither.,it is a hardware unit on the arm-board with a register set
accesed by both arm and
the USBConsole.exe on the PC.This USBConsole.exe sets these registers
appropriately.


> 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?
Setting them on the board memory(USB register memory after virtually mapped)

>     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.
>
  Can a USBConsole.exe running on the windows machine access register on
the arm-board running on the linux.??
>
> As mentioned I am calling the Init_USB function in the start_kernel(after
> Console_Init()).

On Fri, Mar 9, 2012 at 8:34 PM, Greg KH <gregkh at linuxfoundation.org> wrote:

> 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 at vger.kernel.org mailing list, have you tried
> there?
>
> thanks,
>
> greg k-h
>
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