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char: xillybus: Allow 64-bit DMA on PCIe interface

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Until now, only 32-bit DMA addressing was allowed, following a report on
some old Intel machine that dropped 64-bit PCIe packets, even though
pci_set_dma_mask() was successful with DMA_BIT_MASK(64).

But then came TI's Keystone II chip (ARM Cortex A15 + DSPs), which refuses
32-bit DMA addressing (for good reasons). So 64-bit DMA is allowed as a
fallback option.

Signed-off-by: Eli Billauer <eli.billauer@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eli Billauer 2015-08-05 13:03:26 +03:00 committed by Greg Kroah-Hartman
parent f39c4280a3
commit 6497a87573
1 changed files with 6 additions and 4 deletions
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10
drivers/char/xillybus/xillybus_pcie.c
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@ -193,14 +193,16 @@ static int xilly_probe(struct pci_dev *pdev,
}
/*
* In theory, an attempt to set the DMA mask to 64 and dma_using_dac=1
* is the right thing. But some unclever PCIe drivers report it's OK
* when the hardware drops those 64-bit PCIe packets. So trust
* nobody and use 32 bits DMA addressing in any case.
* Some (old and buggy?) hardware drops 64-bit addressed PCIe packets,
* even when the PCIe driver claims that a 64-bit mask is OK. On the
* other hand, on some architectures, 64-bit addressing is mandatory.
* So go for the 64-bit mask only when failing is the other option.
*/
if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(32))) {
endpoint->dma_using_dac = 0;
} else if (!pci_set_dma_mask(pdev, DMA_BIT_MASK(64))) {
endpoint->dma_using_dac = 1;
} else {
dev_err(endpoint->dev, "Failed to set DMA mask. Aborting.\n");
return -ENODEV;