RE: [PATCH 1/2] usb: dwc2: Option to disable dma descriptor mode

[Dinh Nguyen <dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org>]

On Tue, 2014-05-06 at 18:21 +0000, Paul Zimmerman wrote:
> > From: dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org [mailto:dinguyen-EIB2kfCEclfQT0dZR+AlfA@public.gmane.org]
> > Sent: Monday, May 05, 2014 3:23 PM
> > 
> > Even though the IP supports Descriptor DMA mode, it does not support SPLIT
> > transactions in this mode. Since the driver can get the Descriptor DMA mode
> > support from hardware, the driver in its currently form cannot fully support
> > LS/FS devices connected to a HS Hub when Descriptor DMA mode is enabled in the
> > driver. Thus, we give the option to disable Descriptor DMA from device tree.
> 
> Hi Dinh,
> 
> Instead of this patch, how about if we make the driver default to buffer
> DMA mode instead, and if anyone wants to use descriptor DMA mode, they
> can add a DT property for that? I don't think anyone will want that,
> since as you say it doesn't fully support LS/FS devices in that mode.

Yes, I think that's a good idea. Let me spin up a patchset to do that.

Dinh
> 
> The driver originally worked like that. I guess the default got changed by
> one of Matthijs' patches, and I didn't notice it.
> 


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