linux-kernel - Re: [PATCH 3/5] dt-binding: Add Qualcomm WCNSS control binding

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Message-ID: <20160331182449.GA8929@tuxbot>
Date:	Thu, 31 Mar 2016 11:24:49 -0700
From:	Bjorn Andersson <bjorn.andersson@...aro.org>
To:	Rob Herring <robh@...nel.org>
Cc:	Andy Gross <andy.gross@...aro.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	linux-soc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/5] dt-binding: Add Qualcomm WCNSS control binding

On Thu 31 Mar 10:38 PDT 2016, Rob Herring wrote:

> On Thu, Mar 31, 2016 at 12:16 PM, Bjorn Andersson
> <bjorn.andersson@...aro.org> wrote:
> > On Thu 31 Mar 07:28 PDT 2016, Rob Herring wrote:
> >
> >> On Mon, Mar 28, 2016 at 09:35:24PM -0700, Bjorn Andersson wrote:
> > [..]
> 
> [...]
> 
> >> > +
> >> > +== WiFi
> >> > +The following properties are defined to the WiFi node:
> >> > +
> >> > +- compatible:
> >> > +   Usage: required
> >> > +   Value type: <string>
> >> > +   Definition: must be one of:
> >> > +               "qcom,wcn3620-wlan",
> >> > +               "qcom,wcn3660-wlan",
> >> > +               "qcom,wcn3680-wlan"
> >
> > Digging through documentation and trying to answer the questions above
> > made me realize that these numbers are for the external rf component,
> > not the variants of the logic inside the SoC; and as such wrong.
> 
> Do you need to know both? Or only the firmware image needs to know?
> 

So far I've only found cases where we need to know the register map for
the DMA engine shuffling packets, so this is related to the SoC-internal
part only.

The differences in RF capabilities - at least for WiFi - seems to be
acquired in runtime from the firmware.

The other piece that depend on the RF part seems to be the availability
of e.g. ANT support, so if anything that needs to go into the wcnss
node, in some way (either compatible or the set of subnodes).

> >> > +
> >> > +- qcom,wcnss-mmio:
> >> > +   Usage: required
> >> > +   Value type: <prop-encoded-array>
> >> > +   Definition: should specify base address and size of the WiFi related
> >> > +               registers of WCNSS
> >>
> >> This is an address visible to the cpu?
> >>
> >
> > Yes it is; the device is controlled both through SMD and mmio accessible
> > registers, where the SMD interface is the primary interface.
> >
> > SMD being the primary "bus" I believe I can't use reg to denote this
> > register range. Should I describe this in some other form?
> 
> That's a tricky one. I would create a node for the memory-mapped
> portion with proper compatible and reg properties, and then make this
> a phandle to that node. Something similar to how we do phandles to
> syscon's.
> 

Okay, sounds reasonable. I don't see a need for a specific
implementation, so I'll just back it with the generic syscon
implementation (and a specific compatible).

Regards,
Bjorn