RE: [PATCH 04/12] usb: host: ehci-r8a77470: Add EHCI support for Renesas RZ/G1C devices

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On Mon, 1 Apr 2019, Biju Das wrote:

> Hi Alan,
> 
> Thanks for the feedback.
> 
> > Subject: Re: [PATCH 04/12] usb: host: ehci-r8a77470: Add EHCI support for
> > Renesas RZ/G1C devices
> > 
> > On Mon, 1 Apr 2019, Biju Das wrote:
> > 
> > > This patch adds the glue code required to ensure the on-chip EHCI
> > > controller works on RZ/G1C(a.k.a R8A77470) SoC's from Renesas.
> > 
> > You should explain what this new glue code does.  And why is it needed?
> 
> Glue code initializes  following  registers on the host 
> 
> 1) initializing interrupt enable
> 2) OVC detection timer
> 3) suspend/ resume timer register
> 
> Without glue code, interrupt generation is disabled.

Good.  This information should be added to the patch description.

> > Can't you use the existing ehci-platform driver instead?
> > 
> This driver is almost similar to generic ehci-platform except that it needs to do
> some platform initialization as mentioned above. If  I am correct, we cannot do 
> any platform initialization in generic code. 

Are you sure you can't?

Also, have you considered modifying ehci-platform.c, in a 
general-purpose way, such that you could use it and still get this 
platform-specific work done?  For example, you could add some callbacks 
to the usb_ehci_pdata structure.  Or maybe you can use the callbacks 
that are already present, with no modifications needed.

> The reason for the new driver is because of the below discussion
> https://patchwork.kernel.org/patch/10655853/

I didn't notice anything in that discussion which would prevent you 
from using ehci-platform.c (possibly with a few modifications).

Alan Stern




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