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

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Message-ID: <20160331212857.GE8929@tuxbot>
Date:	Thu, 31 Mar 2016 14:28:57 -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 13:42 PDT 2016, Rob Herring wrote:

> On Thu, Mar 31, 2016 at 1:24 PM, Bjorn Andersson
> <bjorn.andersson@...aro.org> wrote:
> > 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).
> 
> I don't think I'd do syscon here as it is mainly designed to have
> multiple users. You just need to look-up the phandle, perhaps check
> the compatible, and call of_address_to_resource to get the address.
> Actually, you could skip the phandle entirely and just find the node
> by compatible (assuming there is only one).
> 

Ahh, right. Thanks for the suggestion.

Regards,
Bjorn