Re: [PATCH 0/3] Implement role-switch notifications from dwc3-drd to dwc3-qcom

From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Felipe Balbi <balbi@kernel.org>
Cc: Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Peter Chen <peter.chen@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	agross@kernel.org, gregkh@linuxfoundation.org,
	jackp@codeaurora.org, wcheng@codeaurora.org,
	linux-usb@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Subject: Re: [PATCH 0/3] Implement role-switch notifications from dwc3-drd to dwc3-qcom
Date: Wed, 15 Sep 2021 08:53:35 -0500	[thread overview]
Message-ID: <YUH639jO4qf4Za/K@yoga> (raw)
In-Reply-To: <87ilzsafu5.fsf@kernel.org>

On Thu 26 Aug 01:15 CDT 2021, Felipe Balbi wrote:

> 
> Hi,
> 
> Bjorn Andersson <bjorn.andersson@linaro.org> writes:
> > On Wed 25 Aug 10:59 PDT 2021, Bryan O'Donoghue wrote:
> >
> >> On 25/08/2021 16:53, Bjorn Andersson wrote:
> >> > But in the case of Type-C altmode several of our boards have either an
> >> > external gpio-based SBU-pin-swapper or some redriver on I2C with this
> >> > functionality, so we need a way to tell both the PHY and this external
> >> > contraption about the orientation.
> >> 
> >> Its a very similar problem to orientation switch
> >> 
> >> As an example
> >> 
> >> - redriver may need to fix up signal integrity for
> >>   lane switching
> >> 
> >> - PHY needs to toggle lanes from one IP block to another
> >> 
> >
> > Right, conceptually the problem is similar, but IMHO there's a big
> > difference in that the redriver and PHY are two physically separate
> > entities - on different buses. The dwc3 glue and core represent the same
> > piece of hardware.
> 
> no they don't. The glue is a real piece of HW that adapts the "generic"
> synopsys IP to a given SoC. OMAP, for example, was adapting Synopsys'
> proprietary interface to the Sonics interconnect, while some others may
> adapt it to AXI or PCI or whatever.
> 
> They are different HW blocks, the glue (in many cases) has its own IRQ,
> its own address space, its own register file, and so on. Granted, the
> glue also serves as an access port from CPU to the synopsys core, but
> that's handled by `ranges' DT property.
> 

So what you're saying is that the "Qualcomm glue" is the hardware, and
the core is just the basis for that design?

Regardless, on the Qualcomm platforms we have need to inform both
devices about role changes, how do we do this? (Without platform_data
and preferably without having to duplicate the typec code in the glue
and core and the two device nodes in DT)

Regards,
Bjorn