Re: [PATCH V2 1/2] mcx: very basic support for HTKW mcx board

["Cousson, Benoit" <b-cousson@ti.com>]

Hi Igor,

On 12/15/2011 10:51 AM, Igor Grinberg wrote:
> On 12/15/11 02:53, Ilya Yanok wrote:
>> Very basic support for HTKW mcx board. Able to boot via board-generic
>> and ramdisk/initramfs, however most of peripherals is unsupported.
>> Produces tons of twl4030 related errors as this board doesn't have
>> twl4030 installed.
>>
>> Signed-off-by: Ilya Yanok<yanok@emcraft.com>
>>
>> ---
>> Changes from V1:
>>
>>   - device tree moved to the separate patch
>>   - iva node is disabled instead of using custom includes
>>   - removed bootargs entry
>>
>>   arch/arm/boot/dts/mcx.dts |   27 +++++++++++++++++++++++++++
>>   1 files changed, 27 insertions(+), 0 deletions(-)
>>   create mode 100644 arch/arm/boot/dts/mcx.dts
>>
>> diff --git a/arch/arm/boot/dts/mcx.dts b/arch/arm/boot/dts/mcx.dts
>> new file mode 100644
>> index 0000000..66b81bd
>> --- /dev/null
>> +++ b/arch/arm/boot/dts/mcx.dts
>> @@ -0,0 +1,27 @@
>> +/*
>> + * Copyright (C) 2011 Ilya Yanok, EmCraft Systems
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + */
>> +/dts-v1/;
>> +
>> +/include/ "omap3.dtsi"
>> +
>> +/ {
>> +	model = "HTKW mcx";
>> +	compatible = "htkw,mcx", "ti,omap3";
>> +
>> +	memory {
>> +		device_type = "memory";
>> +		reg =<0x80000000 0x10000000>; /* 256 MB */
>> +	};
>> +
>> +	/* AM35xx doesn't have IVA */
>> +	soc {
>> +		iva {
>> +			status = "disabled";
>> +		};
>> +	};
>
> I don't get it...
> Why SoCs that do not have those IP blocks should poke
> their configuration inside the h/w description
> (e.g. disable/enable/workaround/hack)?

This is indeed the proper way assuming the HW does contain this 
information. I do not know for this OMAP variant, but this kind of 
information is not necessarily well exposed inside the HW.

> This way, why don't we also disable the PCIe which this SoC does not have?
> Of course, I'm exaggerating, but this just does not scale...
> Soon you will have a bunch of boards disabling stuff,
> that they *do not have natively*...
> Why don't generic OMAP3 DT file disable the EMAC?
> If we will go this way, we will find ourself fixing it later
> and producing the renaming/moving "churn", won't we?

You are indeed exaggerating :-)

Assuming that device is an OMAP3 variant, it seems OK to me to define it 
like that. am35xx = omap3 + (new IPs) - (IPs not supported)

The good point with DT is that you can add or *remove* things from an 
included file.

Regards,
Benoit