Re: [RFC/PATCH 11/14] dt: omap3: add soc file for handling i2c controllers

Cousson, Benoit
2011-08-10T17:45:42Z

+ Tony

On 8/10/2011 6:57 PM, G, Manjunath Kondaiah wrote:
> On Wed, Aug 10, 2011 at 02:36:50PM +0200, Cousson, Benoit wrote:
>> On 8/9/2011 4:10 PM, G, Manjunath Kondaiah wrote:
>>>
>>> Add omap3 soc file for handling omap3 soc i2c controllers existing
>>> on l4-core bus.
>>>
>>> Signed-off-by: G, Manjunath Kondaiah<manjugk@ti.com>
>>> ---
>>> arch/arm/boot/dts/omap3-soc.dtsi | 62 ++++++++++++++++++++++++++++++++++++++
>>> 1 files changed, 62 insertions(+), 0 deletions(-)
>>> create mode 100644 arch/arm/boot/dts/omap3-soc.dtsi
>>>
>>> diff --git a/arch/arm/boot/dts/omap3-soc.dtsi b/arch/arm/boot/dts/omap3-soc.dtsi
>>> new file mode 100644
>>> index 0000000..85de92f
>>> --- /dev/null
>>> +++ b/arch/arm/boot/dts/omap3-soc.dtsi
>>> @@ -0,0 +1,62 @@
>>> +/*
>>> + * Device Tree Source for OMAP3 SoC
>>> + *
>>> + * Copyright (C) 2011 Texas Instruments Incorporated - http://www.ti.com/
>>> + *
>>> + * This file is licensed under the terms of the GNU General Public License
>>> + * version 2. This program is licensed "as is" without any warranty of any
>>> + * kind, whether express or implied.
>>> + */
>>> +
>>> +/dts-v1/;
>>> +/include/ "skeleton.dtsi"
>>> +
>>> +/ {
>>> + #address-cells =<1>;
>>> + #size-cells =<1>;
>>> + model = "ti,omap3";
>>> +
>>> + aliases {
>>> + i2c1 =&i2c1;
>>> + i2c2 =&i2c2;
>>> + i2c3 =&i2c3;
>>> + };
>>> +
>>> + l4-core {
>>
>> That comment is probably subject to discussion, but even if this
>> interconnect is there physically, I'm not sure of the added value to
>> add it.
>> It will add an extra level of indentation and that all. Moreover, it
>> will mess up the physical address that are expressed using absolute
>> value in the TRM with a less readable offset value.
>> In fact, most DTS files in the ARM directory are using a purely flat
>> representation of the interconnect.
> This is as per alignment with Tony and Grant:
> http://permalink.gmane.org/gmane.linux.ports.arm.omap/60391

So I'm asking the same question to Grant and Tony then:-)

>>> + compatible = "ti,omap3-l4-core";
>>
>> Assuming we will keep that, you should probably add a more generic
>> compatible name after that one. Like "ti,s3220" or even
>> "sonics,s3220", assuming that this IP is generic enough for other
>> SoC.
> will check this. I don't remember any generic names.
>>
>>> + #address-cells =<1>;
>>> + #size-cells =<1>;
>>> + ranges =<0 0x48000000 0x1000000>;
>>> +
>>> + i2c1: i2c@70000 {
>>> + #address-cells =<1>;
>>> + #size-cells =<0>;
>>> + compatible = "ti,omap3-i2c";
>>
>> The I2C IP and thus the driver is generic across OMAP generations
>> and is even potentially used by other non-OMAP TI chips like DSP or
>> Davinci. So having an extra compatible entry with "ti,i2c" or "ti,
>> omap-i2c" seems mandatory.
> This can be updated as and when new soc/board adaptations are done.
> As of now, it is omap3 and when we have omap4 it will be appended with
> "ti,omap4-i2c" etc

To infinity and beyond?

There is no need, and we should absolutely not update the driver each
time we introduce a new SoC version/revision.
The driver should match with the generic device name in that case. Until
we change the IP and potentially introduce a new driver.

BTW, even omap3 should not be in the name in theory. It should be
potentially "ti,i2c-v3" or whatever HW version the IP is using.
But for some reason, most devices are using such convention in existing
DTS:-(
This is probably due to the lack of well identified IP version in most
SoC... including OMAP:-)

Benoit