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

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.

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

-- 
Paul

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