linux-kernel - Re: [PATCH v3 2/4] misc: hisi_hikey

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Message-ID: <20210902153820.5624b57f@coco.lan>
Date:   Thu, 2 Sep 2021 15:38:20 +0200
From:   Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Rob Herring <robh@...nel.org>, linuxarm@...wei.com,
        mauro.chehab@...wei.com, John Stultz <john.stultz@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] misc: hisi_hikey_usb: change the DT schema

Em Thu, 2 Sep 2021 15:10:53 +0200
Mauro Carvalho Chehab <mchehab+huawei@...nel.org> escreveu:

> Em Thu, 2 Sep 2021 13:40:28 +0200
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> escreveu:
> 
> > On Thu, Sep 02, 2021 at 01:28:35PM +0200, Mauro Carvalho Chehab wrote:  
> > > As there's no upstream DT bindings for this driver, let's
> > > update its DT schema, while it is not too late.    
> > 
> > So this is for 5.15-final?  
> 
> It can either be for 5.15 or 5.16, as there aren't any compatible
> under arch/ which uses the DT schema there. All patches adding
> such compatible are on this series. So, whatever version this
> is applied should be OK.

On a separate note, despite having "hisi_" on this driver's name, there's
nothing there that is really HiSilicon specific. What this driver does is
to control an USB HUB integrated inside a DT-based board, doing those 
functions:

	- Power on/off the chip;
	- reset the HUB;
	- control its OTG switch;
	- control power on/off for an USB type-C connector;
	- set USB role as host or device.

This is used on both HiKey 960 and HiKey 970 with the following
topology:

  +-----+      +--------+       +---------+
  | SoC | ---> | USB PHY|  ---> | USB HUB | ---> USB 3.0
  +-----+      +--------+       +---------+      and type-C ports 

Both Kirin 960 and 970 SoCs have a Synapsys IP (DWC 3). 

Both HiKey 960 and 970 cards use Richtek RT1711H Type-C Chip Driver
as part of the USB PHY logic, but they use different USB HUBs:

	- HiKey 960 use a Microchip USB5734 HUB
	- HiKey 970 use a TI TUSB8041 HUB

While I'm not sure how generic this driver can be, I'm thinking that
maybe a future patch could rename it to 'generic-usb-hub' or 
something similar - finding a good name is always the hardest 
part :-)

Thanks,
Mauro