linux-kernel - Re: [PATCH 3/3] dt: paz00: define nvec as child of i2c bus

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Message-ID: <551A415B.4040506@mail.ru>
Date:	Tue, 31 Mar 2015 09:40:27 +0300
From:	Andrey Danin <danindrey@...l.ru>
To:	Stephen Warren <swarren@...dotorg.org>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org, ac100@...ts.launchpad.net
CC:	Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Marc Dietrich <marvin24@....de>
Subject: Re: [PATCH 3/3] dt: paz00: define nvec as child of i2c bus

Hi,

Thanks for the review.

On 03.02.2015 0:20, Stephen Warren wrote:
> On 01/29/2015 12:20 AM, Andrey Danin wrote:
>> NVEC driver was reimplemented to use tegra i2c. Use common i2c bindings
>> for NVEC node.
>
>> diff --git a/Documentation/devicetree/bindings/nvec/nvidia,nvec.txt
>> b/Documentation/devicetree/bindings/nvec/nvidia,nvec.txt
>
> The changes to this file make more sense either as a standalone patch
> 1/4, or as part of the driver changes.
>
>> @@ -2,20 +2,5 @@ NVIDIA compliant embedded controller
>>
>>   Required properties:
>>   - compatible : should be "nvidia,nvec".
>> -- reg : the iomem of the i2c slave controller
>> -- interrupts : the interrupt line of the i2c slave controller
>> -- clock-frequency : the frequency of the i2c bus
>> -- gpios : the gpio used for ec request
>> -- slave-addr: the i2c address of the slave controller
>> -- clocks : Must contain an entry for each entry in clock-names.
>> -  See ../clocks/clock-bindings.txt for details.
>> -- clock-names : Must include the following entries:
>> -  Tegra20/Tegra30:
>> -  - div-clk
>> -  - fast-clk
>> -  Tegra114:
>> -  - div-clk
>> -- resets : Must contain an entry for each entry in reset-names.
>> -  See ../reset/reset.txt for details.
>> -- reset-names : Must include the following entries:
>> -  - i2c
>> +- request-gpios : the gpio used for ec request
>> +- reg: the i2c address of the slave controller
>
> This change breaks ABI.
>
> Instead of modifying the definition of the existing compatible value, I
> think you should introduce a new compatible value to describe the
> external NVEC chip.

I changed compatible value to nvec-slave in v2.
>
>> diff --git a/arch/arm/boot/dts/tegra20-paz00.dts
>> b/arch/arm/boot/dts/tegra20-paz00.dts
>
>> -    nvec@...0c500 {
>> -        compatible = "nvidia,nvec";
>> -        reg = <0x7000c500 0x100>;
>> -        interrupts = <GIC_SPI 92 IRQ_TYPE_LEVEL_HIGH>;
>> -        #address-cells = <1>;
>> -        #size-cells = <0>;
>> +    i2c@...0c500 {
>> +        status = "okay";
>>           clock-frequency = <80000>;
>> -        request-gpios = <&gpio TEGRA_GPIO(V, 2) GPIO_ACTIVE_HIGH>;
>> -        slave-addr = <138>;
>> -        clocks = <&tegra_car TEGRA20_CLK_I2C3>,
>> -                 <&tegra_car TEGRA20_CLK_PLL_P_OUT3>;
>> -        clock-names = "div-clk", "fast-clk";
>> -        resets = <&tegra_car 67>;
>> -        reset-names = "i2c";
>> +
>> +        nvec: nvec@45 {
>
> This doesn't feel correct. There's nothing here to indicate that this
> child device is a slave that is implemented by the host SoC rather than
> something external attached to the I2C bus.
>
> Perhaps you can get away with this, since the driver for nvidia,nvec
> only calls I2C APIs suitable for internal slaves rather than external
> slaves? Even so though, I think the distinction needs to be clearly
> marked in the DT so that any generic code outside the NVEC driver that
> parses the DT can determine the difference.
>
> I would recommend the I2C controller having #address-cells=<2> with cell
> 0 being 0==master,1==slave, cell 1 being the I2C address. The I2C driver
> would need to support #address-cells=<1> for backwards-compatibility.
>
Driver (nvec in this case) can decide what mode should it use according 
to compatible value. Is it not enough ?

>> +            compatible = "nvidia,nvec";
>> +            request-gpios = <&gpio TEGRA_GPIO(V, 2)
>> +                GPIO_ACTIVE_HIGH>;
>> +            reg = <0x45>;
>
> The order is typically compatible, reg, other properties.

Ok, thanks.
>
>> +        };
>>       };
>

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