Re: [PATCH v1 1/2] usb:dwc3: Enable support for 64-bit system

From	Felipe Balbi <balbi@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v1 1/2] usb:dwc3: Enable support for 64-bit system
Date	2016-01-16 04:30 +0100
Message-ID	<qRpIR-76j-5@gated-at.bofh.it> (permalink)
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Hi,

"Thang Q. Nguyen" <tqnguyen@apm.com> writes:
> Hi Balbi,
>
> On Thu, Jan 14, 2016 at 10:47 PM, Felipe Balbi <balbi@kernel.org> wrote:
>>
>>
>> Hi,
>>
>> "Thang Q. Nguyen" <tqnguyen@apm.com> writes:
>> > Add 64-bit DMA operation support to the USB DWC3 driver.
>> > First attempt to set the coherent DMA mask for 64-bit DMA.
>> > If that failed, attempt again with 32-bit DMA.
>> >
>> > Signed-off-by: Thang Q. Nguyen <tqnguyen@apm.com>
>> > ---
>> >  drivers/usb/dwc3/core.c | 15 +++++++++++++++
>> >  1 file changed, 15 insertions(+)
>> >
>> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> > index 22b47973..9818d6b 100644
>> > --- a/drivers/usb/dwc3/core.c
>> > +++ b/drivers/usb/dwc3/core.c
>> > @@ -829,6 +829,21 @@ static int dwc3_probe(struct platform_device *pdev)
>> >       dwc->mem = mem;
>> >       dwc->dev = dev;
>> >
>> > +     /* Try to set 64-bit DMA first */
>> > +     if (WARN_ON(!pdev->dev.dma_mask))
>>
>> why the WARN_ON() ?
>
> In my opinion, pdev->dev.dma_mask is expected to be set correctly. And

sure is, but a WARN_ON() will print out a stack dump, which looks
scary. Besides, if it's not set you're already fixing the problem.

> the issue happen just in case of DT boot and CONFIG_DMA_CMA=n, the
> pdev->dev.dma_mask value is not set. So, I set WARN_ON there to notify

why isn't it set ?

> that we expect pdev->dev.dma_mask set but not.

why don't you fix that case, instead ?

-- 
balbi

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Re: [PATCH v1 1/2] usb:dwc3: Enable support for 64-bit system Felipe Balbi <balbi@kernel.org> - 2016-01-16 04:30 +0100
  Re: [PATCH v1 1/2] usb:dwc3: Enable support for 64-bit system "Thang Q. Nguyen" <tqnguyen@apm.com> - 2016-01-16 05:10 +0100

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