The fsl_mxc_udc driver was originally developed as a part of a DENX
project, adding Marek to CC to have them check internally what their
preferences and requirements might be.
Thanks
Guennadi
On Fri, 11 Jun 2021, Leo Li wrote:
> > -----Original Message-----
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> > Sent: Friday, June 11, 2021 10:43 AM
> > To: Fabio Estevam <festevam@xxxxxxxxx>
> > Cc: gregkh <gregkh@xxxxxxxxxxxxxxxxxxx>; Felipe Balbi <balbi@xxxxxxxxxx>;
> > Joel Stanley <joel@xxxxxxxxx>; Leo Li <leoyang.li@xxxxxxx>; kbuild test
> > robot <lkp@xxxxxxxxx>; Peter Chen <peter.chen@xxxxxxx>; Ran Wang
> > <ran.wang_1@xxxxxxx>; Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>;
> > Shawn Guo <shawnguo@xxxxxxxxxx>; # 3.4.x <stable@xxxxxxxxxxxxxxx>;
> > Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > Subject: Re: patch "Revert "usb: gadget: fsl: Re-enable driver for ARM SoCs""
> > added to usb-linus
> >
> > On Fri, Jun 11, 2021 at 4:51 PM Fabio Estevam <festevam@xxxxxxxxx> wrote:
> > > On Fri, Jun 11, 2021 at 5:30 AM Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > >
> > > > Adding Fabio and Guennadi to Cc.
> > > >
> > > > I can see that the missing symbols were in a driver that got removed
> > > > in commit a390bef7db1f ("usb: gadget: fsl_mxc_udc: Remove the driver").
> > > >
> > > > If CONFIG_ARCH_MXC is disabled, these are stubbed out in the header
> > file.
> > > > These were added a long time ago by Guennadi Liakhovetski
> > > > 54e4026b64a9
> > > > ("USB: gadget: Add i.MX3x support to the fsl_usb2_udc driver"). I
> > > > also see that this patch added a few #ifdef CONFIG_ARCH_MXC checks
> > > > to the driver that still remain today. This is clearly broken as it
> > > > must be possible to use the same driver module on both SOC_LS1021A
> > > > and i.MX using a runtime check.
> > > >
> > > > I also don't see any i.MX variant actually using this driver, but
> > > > instead see the dts files declaring fsl,imx27-usb devices, which
> > > > bind to the drivers/usb/chipidea/ci_hdrc_imx.c driver. Is this one
> > > > of those cases where we have two separate drivers for the same
> > > > hardware, or is this for a different device?
> > >
> > > Exactly. The USB IP on several i.MX devices comes from ChipIdea.
> > >
> > > Prior to using devicetree, we had the fsl_mxc_udc driver to handle the
> > > gadget side.
> > >
> > > Since i.MX has been converted to a DT-only platform, we no longer need
> > > fsl_mxc_udc, as drivers/usb/chipidea is used nowadays.
> >
> > Ok, good, so the simples solution I suppose is to remove the remaining bits
> > that Guennadi added when he wrote the removed driver in 54e4026b64a9,
> > and then re-apply Joel's patch.
>
> I can provide a patch for this.
>
> >
> > Alternatively, it might be possible change the chipidea driver to work on
> > ls1021a and ls1012a, assuming that they use the same hardware block as i.MX.
>
> It is also used on many legacy FSL PowerPC SoCs. I agree with the direction, but it does require some effort to make sure it works on all these legacy platforms. I think Ran Wang had tried to do that, but not completed due to bandwidth issue.
>
> >
> > Either way, it would be good to test the changes on at least one of these two
> > platforms.
> >
> > Arnd
>
