Re: [PATCH v4 2/4] usb: dwc2: add compatible data for rockchip soc

[Kever.Yang]

On 08/08/2014 04:52 AM, Doug Anderson wrote:
> Paul,
>
> On Thu, Aug 7, 2014 at 11:26 AM, Paul Zimmerman
> <Paul.Zimmerman@xxxxxxxxxxxx> wrote:
> > > From: Kever Yang [mailto:kever.yang@xxxxxxxxx] On Behalf Of Kever Yang
> > > Sent: Thursday, August 07, 2014 2:35 AM
> > >
> > > This patch add compatible data for dwc2 controller found on
> > > rk3066, rk3188 and rk3288 processors from rockchip.
> > >
> > > Signed-off-by: Kever Yang <kever.yang@xxxxxxxxxxxxxx>
> > > Acked-by: Paul Zimmerman <paulz@xxxxxxxxxxxx>
> > > ---
> > >
> > > Changes in v4:
> > > - max_transfer_size change to 65536, this should be enough
> > >    for most transfer, the hardware auto-detect will set this
> > >    to 0x7ffff which may make dma_alloc_coherent fail when
> > >    non-dword aligned buf from driver like usbnet happen.
> > Hi Kever,
> >
> > Did you test this change thoroughly? I have vague memories of any
> > value above 65535 causing problems, at least on my hardware. And I
> > see it is set to 65535 in both pci.c and platform.c. I could be
> > wrong, but I thought I should mention it.
> Certainly it is documented in the header file to have a max of 65535:
>
>   * @max_transfer_size:  The maximum transfer size supported, in bytes
>   *                       2047 to 65,535
>   *                      Actual maximum value is autodetected and also
>   *                      the default.
Sorry for didn't check the header file, I'll change it to 65535 and 
resubmit.
> ...but looking at the register definition that I see, the size can be
> up to 19 bits.  A 19-bit transfer far exceeds 65535.  Do you remember
> what the error was?  Certainly I can imagine there being errors with
> large calls to dma_alloc_coherent()...
>
> I know that with Kever's change I can do USB Ethernet downloads, so it
> is at least working to some degree.  ...to me it feels like Kever
> should resubmit with 65535 (to match the documentation) and then work
> in the background to figure out what the max_transfer_size really
> ought to be.
You are right.
> -Doug


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