Messages in this thread | | | Date | Tue, 26 Mar 2013 19:56:53 +0100 | From | Stefan Richter <> | Subject | Re: [PATCH] firewire: Enable physical DMA above 4GB |
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On Mar 26 Peter Hurley wrote: > Quadlet reads to memory above 4GB is painfully slow when serviced > by the AR DMA context. In addition, the CPU(s) may be locked-up, > preventing any transfer at all. > > Write the PhyUpperBound register with the end-of-memory value. If > end-of-memory is beyond the OHCI limit of 0x0000ffff00000000, > clamp to that value. > > Signed-off-by: Peter Hurley <peter@hurleysoftware.com> > --- > drivers/firewire/ohci.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c > index 044ace3..b4135a5 100644 > --- a/drivers/firewire/ohci.c > +++ b/drivers/firewire/ohci.c > @@ -2249,6 +2249,7 @@ static int ohci_enable(struct fw_card *card, > struct pci_dev *dev = to_pci_dev(card->device); > u32 lps, version, irqs; > int i, ret; > + u32 phys_upper; > > if (software_reset(ohci)) { > dev_err(card->device, "failed to reset ohci card\n"); > @@ -2323,7 +2324,10 @@ static int ohci_enable(struct fw_card *card, > reg_write(ohci, OHCI1394_FairnessControl, 0); > card->priority_budget_implemented = ohci->pri_req_max != 0; > > - reg_write(ohci, OHCI1394_PhyUpperBound, 0x00010000); > + phys_upper = min(0xffff0000ULL, > + (dma_get_required_mask(card->device) >> 16) + 1); > + reg_write(ohci, OHCI1394_PhyUpperBound, max(phys_upper, 0x00010000U)); > + > reg_write(ohci, OHCI1394_IntEventClear, ~0); > reg_write(ohci, OHCI1394_IntMaskClear, ~0); >
What Clemens said.
Also: By far most OHCI-1394 chips do not implement PhyUpperBound, i.e. ignore any writes to PhyUpperBound, return 0 when PhyUpperBound is read, and keep the boundary between physical response and AR response at 4 GB, as described in the spec.
It has been a long time though since I last checked whether PhyUpperBound is implemented; maybe it has become more widespread than it was back then.
Or maybe it hasn't: All OHCI-1394 chips that ever came to market are 32 bit chips anyway. So the few rare ones that do support PhyUpperBound larger than 4 GB cannot in fact use it.
Or am I severely behind the times about this? -- Stefan Richter -=====-===-= --== ==-=- http://arcgraph.de/sr/
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