Timur,
I think, the device driver is responsible for setting the right DMA_MASK
based on the underlying hardware capability if your driver wants to
support 64bit DMA.
Example code in drivers/usb/host/xhci.c:
/* Set dma_mask and coherent_dma_mask to 64-bits,
* if xHC supports 64-bit addressing */
if (HCC_64BIT_ADDR(xhci->hcc_params) &&
!dma_set_mask(dev, DMA_BIT_MASK(64))) {
xhci_dbg(xhci, "Enabling 64-bit DMA addresses.\n");
dma_set_coherent_mask(dev, DMA_BIT_MASK(64));
} else {
/*
* This is to avoid error in cases where a 32-bit USB
* controller is used on a 64-bit capable system.
*/
retval = dma_set_mask(dev, DMA_BIT_MASK(32));
On 06/20/2016 12:41 PM, Timur Tabi wrote:
Rob Herring wrote:
>+ dma-ranges = <0 0 0xffffffff>;
I believe dma-ranges is supposed to be in the bus (parent) node.
Maybe I'm just going to be perpetually confused by dma-ranges, but how
can I specify that the emac has a different DMA range from another SOC
device, if dma-ranges is in the parent node?
The EMAC itself is capable of 64-bit DMA internally (I should have
included a dma_set_mask call with DMA_BIT_MASK(64) in the driver).
However, the platform typically limits this range. On FSM9900 and
QDF2432, it's 32 bits. On the next server chip, it'll be the full 64
bits. I need some way to handle that.
--
Shanker Donthineni
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
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