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Date: Wed, 31 Aug 2016 13:22:34 +0200
From: Mirza Krak <mirza.krak@...il.com>
To: Rob Herring <robh@...nel.org>
Cc: Jon Hunter <jonathanh@...dia.com>,
Stephen Warren <swarren@...dotorg.org>,
Thierry Reding <thierry.reding@...il.com>,
Alexandre Courbot <gnurou@...il.com>, linux@...linux.org.uk,
pdeschrijver@...dia.com, Prashant Gaikwad <pgaikwad@...dia.com>,
Michael Turquette <mturquette@...libre.com>,
sboyd@...eaurora.org, mark.rutland@....com,
devicetree@...r.kernel.org, linux-tegra@...r.kernel.org,
linux-kernel <linux-kernel@...r.kernel.org>,
linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 3/6] dt/bindings: Add bindings for Tegra GMI controller
2016-08-30 19:06 GMT+02:00 Rob Herring <robh@...nel.org>:
> On Wed, Aug 24, 2016 at 09:54:47PM +0200, Mirza Krak wrote:
>> 2016-08-24 17:56 GMT+02:00 Jon Hunter <jonathanh@...dia.com>:
>> +
>> >> +Example with two SJA1000 CAN controllers connected to the GMI bus. We wrap the
>> >> +controllers with a simple-bus node since they are all connected to the same
>> >> +chip-select (CS4), in this example external address decoding is provided:
>> >> +
>> >> +gmi@...90000 {
>> >> + compatible = "nvidia,tegra20-gmi";
>> >> + reg = <0x70009000 0x1000>;
>> >> + #address-cells = <1>;
>> >> + #size-cells = <1>;
>> >> + clocks = <&tegra_car TEGRA20_CLK_NOR>;
>> >> + clock-names = "gmi";
>> >> + resets = <&tegra_car 42>;
>> >> + reset-names = "gmi";
>> >> + ranges = <4 0x48000000 0x7ffffff>;
>> >> +
>> >> + status = "disabled";
>> >> +
>> >> + bus@4 {
>> >> + compatible = "simple-bus";
>> >> + reg = <4>;
>> >> + #address-cells = <1>;
>> >> + #size-cells = <1>;
>> >> + ranges = <0 4 0x40100>;
>> >
>> > Does this work? I tried to add an example like this and I got ...
>> >
>> > Warning (reg_format): "reg" property in /gmi@...09000/bus@4 has invalid
>> > length (4 bytes) (#address-cells == 1, #size-cells == 1)
>>
>> Shoot, to get rid of the warning it should be
>>
>> reg = <4 0 >;
>>
>> But it works either way.
>
> The CS node should have #address-cells=2 with the first being CS# and
> the second being the offset (often 0).
>
>>
>> >
>> > I am wondering if we should just following the arm,pl172 example and
>> > have ...
>> >
>> > cs4 {
>> > compatible = "simple-bus";
>> > #address-cells = <1>;
>> > #size-cells = <1>;
>> > ranges;
>
> Empty ranges is typically wrong and due to laziness...
>
> This should have the CS# in it.
>
>> >
>> > nvidia,snor-cs = <4>;
>> > nvidia,snor-mux-mode;
>> > nvidia,snor-adv-inv;
>> >
>> > can@0 {
>> > reg = <0 0x100>;
>
> This can be 1 cell with just the offset.
>
>> > ...
>> > };
>> >
>> > ...
>> > };
>> >
>>
>> That means to go back to V1 really (almost :)). Which I do not mind.
>> Will give it a test run.
>>
>> But I am a little hesitant if will be any better/cleaner. In your example above:
>>
>> can@0 {
>> reg = <0 0x100>;
>> ...
>> };
>>
>> Would this really translate correctly? In the pl172 example they have
>> multiple ranges and address with "flash@0,0" which a range defined in
>> parent node. "can@0" does not have valid match in parent node in our
>> example. So I probably need add some more logic for it to properly
>> translate.
>
> pl172 has several things I don't like, so don't follow it. Mainly those
> are custom CS property and 3 levels of nodes. I'm fine with 3 levels if
> there is more than one device, but otherwise 2 levels with timing
> properties in the child device node.
>
>
>>
>> I have an idea which is following:
>>
>> gmi@...90000 {
>> status = "okay";
>> #address-cells = <2>;
>> #size-cells = <1>;
>> ranges = <4 0 0x48000000 0x00040000>;
>>
>> cs4 {
>
> cs@4,0
>
>> compatible = "simple-bus";
>> #address-cells = <2>;
>
> 1 cell here.
>
>> #size-cells = <1>;
>> ranges;
>
> Fill this in to drop the 2nd cell on child addresses and just have the
> offset.
>
>>
>> nvidia,snor-cs = <4>;
>
> NAK, no custom CS properties.
>
>> nvidia,snor-mux-mode;
>> nvidia,snor-adv-inv;
>>
>> can@0 {
>> compatible = "nxp,sja1000";
>> reg = <4 0 0x100>;
>> ...
>> };
>>
>>
>> can@...00 {
>> compatible = "nxp,sja1000";
>> reg = <4 0x40000 0x100>;
>> ...
>> };
>> };
>> };
>>
Thank you for your review Rob.
Taking your comments in to account I end up with this:
gmi@...90000 {
compatible = "nvidia,tegra20-gmi";
reg = <0x70009000 0x1000>;
#address-cells = <2>;
#size-cells = <1>;
clocks = <&tegra_car TEGRA20_CLK_NOR>;
clock-names = "gmi";
resets = <&tegra_car 42>;
reset-names = "gmi";
ranges = <4 0 0xd0000000 0xfffffff>;
status = "okay";
bus@4,0 {
compatible = "simple-bus";
#address-cells = <1>;
#size-cells = <1>;
ranges = <0 4 0 0x40000>;
nvidia,snor-mux-mode;
nvidia,snor-adv-inv;
can@0 {
reg = <0 0x100>;
...
};
can@...00 {
reg = <0x40000 0x100>;
...
};
};
};
Have I understood you correct?
Also wanted to verify the example case where you only have on device
connected to one CS#, from what I see in other implementations it
seems OK to put the CS# in the reg property in that case. Is this
correct?
Example with one SJA1000 CAN controller connected to the GMI bus
on CS4:
gmi@...90000 {
compatible = "nvidia,tegra20-gmi";
reg = <0x70009000 0x1000>;
#address-cells = <2>;
#size-cells = <1>;
clocks = <&tegra_car TEGRA20_CLK_NOR>;
clock-names = "gmi";
resets = <&tegra_car 42>;
reset-names = "gmi";
ranges = <4 0 0xd0000000 0xfffffff>;
status = "okay";
can@4,0 {
reg = <4 0 0x100>;
nvidia,snor-mux-mode;
nvidia,snor-adv-inv;
...
};
};
Jon, to be able to handle both cases in the driver we would first
attempt to decode the CS# from the ranges property, and fallback to
reg property if no ranges are defined. Does that sound reasonable?
Best Regards
Mirza
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