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Commit 6497a875 authored by Eli Billauer's avatar Eli Billauer Committed by Greg Kroah-Hartman
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char: xillybus: Allow 64-bit DMA on PCIe interface 



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: default avatarEli Billauer <eli.billauer@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent f39c4280

drivers/char/xillybus/xillybus_pcie.c

+6 −4
Original line number Diff line number Diff line
@@ -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;