linux-kernel - Re: [PATCH v3 1/3] soc: devicetree: bindings: Add Qualcomm RPM DT binding

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Message-ID: <53A14F00.9010904@linaro.org>
Date:	Wed, 18 Jun 2014 09:34:08 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>
CC:	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Kumar Gala <galak@...eaurora.org>,
	Lee Jones <lee.jones@...aro.org>,
	Josh Cartwright <joshc@...eaurora.org>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 1/3] soc: devicetree: bindings: Add Qualcomm RPM DT
 binding



On 18/06/14 00:59, Stephen Boyd wrote:
> On 06/16/14 11:46, Bjorn Andersson wrote:
>> diff --git a/Documentation/devicetree/bindings/soc/qcom/qcom,rpm.txt b/Documentation/devicetree/bindings/soc/qcom/qcom,rpm.txt
>> new file mode 100644
>> index 0000000..0366533
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/soc/qcom/qcom,rpm.txt
>> @@ -0,0 +1,260 @@
>> +Qualcomm Resource Power Manager (RPM)
>> +
> [...]
>> +
>> +- reg:
>> +	Usage: required
>> +	Value type: <prop-encoded-array>
>> +	Definition: two entries specifying the RPM's message ram and ipc register
>> +
>> +- reg-names:
>> +	Usage: required
>> +	Value type: <string-array>
>> +	Definition: must contain the following, in order:
>> +		    "msg_ram"
>> +		    "ipc"
>
> ipc is concerning....
>
>> +	rpm@...000 {
>> +		compatible = "qcom,rpm-msm8960";
>> +		reg = <0x108000 0x1000 0x2011008 0x4>;
>> +
>
> (reg-names is missing from the example)
>
> because ipc is actually a register inside the Krait complex's global
> clock control/distribution hardware block (it's located at 0x2011000).
>  From what I can tell, this is the only non-clock/power register inside
> there. I plan to send out a driver for this hardware block so that I can
> switch the L2 aux source mux over to PLL8 instead of PXO (done with a
> single register write to 0x2011028) and this mapping/use here is going
> to conflict with that unless I only map the single register like is done
> here.
>
> I wonder if we'd be better off making this region a separate node and
> having some phandle to it here in the RPM node? That way we have a

Can't we use syscon based on regmap here?  syscon is a better way to 
share a common register space across multiple drivers.

> driver that provides a clock and some IPC handle the RPM driver can get.
> The SMD driver also uses the same register to kick other processors so
> having some generic IPC handle may be useful there too.
>
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