On Thu, Apr 29, 2010 at 09:55:05AM -0400, Charles Brown wrote:
> 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.
You want to use dma_alloc_coherent() since it's going to be a
persistent mapping and will be re-used, albeit only for PCI->host
transfers.
> At this point, my best reference has been discarded, and I'm looking
> for another.
I don't know of any other devices that have exactly this behavior.
It sounds like a data acquisition device and you might find others.
> 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.
Sorry - I've not been available lately. I see someone else
already replied (which I haven't read yet). I'll reply again
if I have anything else to add tomorrow (Sunday).
cheers,
grant
>
> --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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