linux-kernel - Re: [PATCH] drivers: usb: dwc3 : Configure DMA properties and ops from DT

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Message-ID: <CADRPPNQvRrWOHTGQUyKatuB03TwrC+tQbO50A_TNJL47wp+60Q@mail.gmail.com>
Date:	Thu, 26 May 2016 15:56:50 -0500
From:	Leo Li <pku.leo@...il.com>
To:	Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc:	Rajesh Bhagat <rajesh.bhagat@....com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Li Yang <leoyang.li@....com>, sriram.dash@....com
Subject: Re: [PATCH] drivers: usb: dwc3 : Configure DMA properties and ops
 from DT

On Thu, May 26, 2016 at 3:30 AM, Felipe Balbi
<felipe.balbi@...ux.intel.com> wrote:
>
> Hi,
>
> Leo Li <pku.leo@...il.com> writes:
>>>> On certain platforms (e.g. ARM64) the dma_ops needs to be explicitly set
>>>> to be able to do DMA allocations, so use the of_dma_configure() helper
>>>> to populate the dma properties and assign an appropriate dma_ops.
>>>>
>>>> Signed-off-by: Rajesh Bhagat <rajesh.bhagat@....com>
>>>> Reviewed-by: Yang-Leo Li <leoyang.li@....com>
>>>
>>> Cool, nxp is also using dwc3 :-) C'mon Rajesh, send us a glue layer :)
>>>
>>>> diff --git a/drivers/usb/dwc3/host.c b/drivers/usb/dwc3/host.c
>>>> index c679f63..4d5b783 100644
>>>> --- a/drivers/usb/dwc3/host.c
>>>> +++ b/drivers/usb/dwc3/host.c
>>>> @@ -17,6 +17,7 @@
>>>>
>>>>  #include <linux/platform_device.h>
>>>>  #include <linux/usb/xhci_pdriver.h>
>>>> +#include <linux/of_device.h>
>>>>
>>>>  #include "core.h"
>>>>
>>>> @@ -32,6 +33,9 @@ int dwc3_host_init(struct dwc3 *dwc)
>>>>               return -ENOMEM;
>>>>       }
>>>>
>>>> +     if (IS_ENABLED(CONFIG_OF) && dwc->dev->of_node)
>>>> +             of_dma_configure(&xhci->dev, dwc->dev->of_node);
>>>
>>> okay, so we have a long discussion about this going on. You can catch up
>>> with it starting here:
>>>
>>> http://marc.info/?i=1461612094-30939-1-git-send-email-grygorii.strashko@ti.com
>>>
>>> At least for now, this patch will be applied. We need to have a better
>>> solution for this, one that helps not only DT platforms.
>>
>> Balbi,
>>
>> Has the patch from Grygorii been applied?  I don't see it in the
>> mainline tree yet.  Without fix, the dwc3 driver will fail for all
>> ARM64 SoCs.
>
> right, it's still broken. But we don't want something that fixes only
> OF, right? dwc3 is also broken for PCI when IOMMU is enabled. It breaks
> for the same reasons.
>
> We really need a way to inherit DMA bits from parent device here.

I agree with your proposal, but the original discussion seems to be on
halt right now.  If it need more time to get to an agreement on proper
fix, probably it's better to have a temporary fix right now to make
the driver working again.

Regards,
Leo