From 6497a8757361a88b73fc3814d2ee9b9fc105fa42 Mon Sep 17 00:00:00 2001 From: Eli Billauer Date: Wed, 5 Aug 2015 13:03:26 +0300 Subject: [PATCH] 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: Eli Billauer Signed-off-by: Greg Kroah-Hartman --- drivers/char/xillybus/xillybus_pcie.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/drivers/char/xillybus/xillybus_pcie.c b/drivers/char/xillybus/xillybus_pcie.c index d8266bc2ae35..9418300214e9 100644 --- a/drivers/char/xillybus/xillybus_pcie.c +++ b/drivers/char/xillybus/xillybus_pcie.c @@ -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; -- 2.39.5