Grant,
Early on I was using the altpciechdma driver as reference, but the
hardware engineer doesn't want me controlling the DMA on the card. So,
we're just using memcpy_toio/fromio.
That design also has the card providing host->board IO memory using
BAR0 and board->host using BAR2, but the HW engineer only wants to
provide host->board memory in BAR0, and me to provide the memory for
board->host - by allocating appropriate memory and handing back a
physical address. He has BAR2 set to 0.
At this point, my best reference has been discarded, and I'm looking
for another. So, I'll track down the two you mention. In the
meanintime, my code snippets are below - I've left out all my debug
printk's and error checking cruft. The iomstart is an address
calculated from /proc/iomem, hence my mis-calling it "I/O memory".
Thank you for spending some time with me on this.
--CB
/** start address for iomem block to allocate for read space */
unsigned long iomstart = 0, iomlength = 0;
module_param(iomstart,ulong,0);
module_param(iomlength,ulong,0);
...snip...
void alt_onInit(void)
{
int i, status = 0;
struct resource * resource = NULL;
/* request IO memory for incoming data */
resource = request_mem_region(iomstart, iomlength, DEVNAME);
...snip...
int
alt_probe(struct pci_dev *dev, const struct pci_device_id *id)
{
...snip...
/* get BAR0 addresses */
start = pci_resource_start(board->dev, 0);
end = pci_resource_end(board->dev, 0);
size = (end - start);
/* write address back, so board can use it in address translation */
dest = (unsigned char *)ioremap( start, size );
memcpy_toio( &dest[4], &board->iomstart, sizeof(board->iomstart) );
memcpy_toio( &dest[4+sizeof(board->iomstart)], &board->iomlength,
sizeof(board->iomlength) );
memcpy_toio( &dest[0], "RDY\0", 4 );
iounmap( dest );
...snip...
/* Read data from the altera board. */
void alt_read( size_t boardno )
{
...snip...
/* get board addresses */
start = board->iomstart;
size = board->iomlength;
/* read data board has written into host IO memory */
src = (unsigned char *)ioremap( start, size );
memcpy_fromio( dest, src, 256 );
iounmap( src );
Grant Grundler wrote:
On Tue, Apr 27, 2010 at 04:48:40PM -0400, Charles Brown wrote:
> All,
>
> I'm trying to write a device driver under ubuntu for a PCI card, and
> exchange information with the card.
>
> The hardware engineer has configured the card to support BAR0 for
> data to the card, and linux allocates memory at kernel boot and I am
> able to write data from the driver to the card.
>
> For data coming from the card to the driver, the hardware engineer
> expects the driver to allocate IO memory when the driver loads, and to
> provide the physical address of that memory to the card - which the card
> will use with its address translation register, to write data directly
> into the provided I/O memory.
I think you are confused here. "I/O Memory" is on the card. Your engineer
is telling you he wants the card to transfer data to *host* memory.
The card needs a "PCI Bus Address" (aka "physical address") to access
that memory and Documentation/DMA-API.txt will explain that to you.
> Using information from LDD3 I've been able to allocate IO memory, but
> I can't find any PCI/kernel functions that allow me to tell the kernel
> about this memory for the PCI card, and there's no way to tell the card
> about this memory, except through writing the physical address back into
> the IO memory associated to BAR0.
>
> How do I make this allocated memory available to the card?
See how other drivers use interfaces described in Documentation/DMA-API.txt.
e.g. drivers/net/bnx2 or drivers/scsi/mpt2sas
It would be helpful if you could post the code some place. Assuming you
can't and this driver will be released under GPL, just copy code from a
similar driver.
hth,
grant
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