Re: [RFC PATCH 0/7] usb: dwc2 host driver

[Jules Maselbas <jmaselbas@kalray.eu>]

On Tue, Jan 14, 2020 at 03:27:04PM +0100, Sascha Hauer wrote:
> Hi Jules,
> 
> On Tue, Jan 14, 2020 at 02:21:05PM +0100, Jules Maselbas wrote:
> > Hi Sascha,
> > 
> > I've been working on a driver for the dwc2 otg controller, for both host
> > and device mode.  Like you I've started from U-Boot driver and I mixed
> > it with some part from Linux.  For instance I've removed the register
> > structs and I've been using the same defines for register bit-fields as
> > in Linux.
> > 
> > I would like to share my version of the host driver, as the gadget driver
> > one still requires some cleanup.  This series is not to be applied on the
> > driver you proposed. However I am willing to propose a new series that can
> > be applied on the driver you proposed.  What do you think?
> 
> The dwc2 driver was a quick shot, I am all in for improvements. Removing
> the register structs is very nice and I would be interested in gadget
> support as well.
The gadget support is almost ready, I got the dfu gadget working. :) 
 
> What SoC are you using the driver on?
I am using this driver on our custom SoC, the Kalray Coolidge MPPA (k1c).
I didn't tried on other SoC.

> I am not sure if it makes sense to rebase your patches on my driver. If
> you can convince me that yours is better then we could just remove mine
> and merge yours instead.
I don't have a strong argument in favor of my version. Except that I have
already made some changes over the original U-Boot version: 

I've tried to improve the roothub interface making it easier to decode
new requests.

I have removed the memcpy done in transfer_chunk between the usb data
buffer and the dma buffer :/
However this mean that all buffer used for usb tranfert must be dma
capable.  Not all usb transfers use dma_alloc for it's buffers but
sometime they are allocated on the stack, this can be problematic if
the stack cannot be used by DMA.

I also have fixed an error in the handling of the toggle bit, but I
think the solution is a bit hacky. I think the driver should rather
use the toggle bit stored in the usb_device structure, but this will
require more rework.

If theses changes make sense then let's use this version.

Best,
Jules

> Sascha
> 
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