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SubjectRe: [PATCH] usb: dwc3: host: inherit dma configuration from parent dev
On 04/27/2016 08:41 AM, Felipe Balbi wrote:
> Hi,
> Grygorii Strashko <> writes:
>> On 04/26/2016 09:17 AM, Felipe Balbi wrote:
>>> Hi,
>>> Grygorii Strashko <> writes:
>>>> Now not all DMA paremters configured properly for "xhci-hcd" platform
>>>> device which is created manually. For example: dma_pfn_offset, dam_ops
>>>> and iommu configuration will not corresponds "dwc3" devices
>>>> configuration. As result, this will cause problems like wrong DMA
>>>> addresses translation on platforms with LPAE enabled like Keystone 2.
>>>> When platform is using DT boot mode the DMA configuration will be
>>>> parsed and applied from DT, so, to fix this issue, reuse
>>>> of_dma_configure() API and retrieve DMA configuartion for "xhci-hcd"
>>>> from DWC3 device node.
>>> patch is incomplete. You left out non-DT users which might suffer from
>>> the same problem.
>> Honestly, I don't know how to fix it gracefully for non-DT case.
>> I can update commit message to mention that this is fix for DT case only.
> no, that won't do :-) There are other users for this driver and they are
> all "out-of-compliance" when it comes to DMA usage. Apparently, the
> desired behavior is to pass correct device to DMA API which the gadget
> side is already doing (see below). For the host side, the fix has to be
> more involved.
> Frankly, I'd prefer that DMA setup could be inherited from parent
> device, then it wouldn't really matter and a bunch of this could be
> simplified. Some sort of dma_inherit(struct device *dev, struct device
> *parent) would go a long way, IMHO.
> 8<-------------------------------- cut here ------------------------
> commit 2725d6f974c4c268ae5fb746f8e3b33b76135aa8
> Author: Felipe Balbi <>
> Date: Tue Apr 19 16:18:12 2016 +0300
> usb: dwc3: use parent device for DMA
> our parent device is the one which was initialized
> by either PCI or DeviceTree and that's the one which
> is configured properly for DMA access.
> Instead of copying DMA bits from parent to child,
> let's just rely on parent device for the entire DMA
> API.

1) Patch I've sent fixes "xhci-hcd" platform device and not dwc3 core.
On TI boards dwc3 core devices are created from DT and so, I do not see
any problems with dwc3 core. Problem is with xhci.

2) there is minimum one dtsi file where dwc3 ("snps,dwc3") does not have parent device
ls1021a.dtsi (and 5 dtsi in arm64 folder)

> Signed-off-by: Felipe Balbi <>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index c050a88c16d4..09e4ff71a50f 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -180,7 +180,7 @@ static void dwc3_frame_length_adjustment(struct dwc3 *dwc, u32 fladj)
> static void dwc3_free_one_event_buffer(struct dwc3 *dwc,
> struct dwc3_event_buffer *evt)
> {
> - dma_free_coherent(dwc->dev, evt->length, evt->buf, evt->dma);
> + dma_free_coherent(dwc->dev->parent, evt->length, evt->buf, evt->dma);
> }



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