Re: [PATCH 4/4] ARM: dts: keystone-k2hk: add dsp gpio controllers nodes

[Grygorii Strashko <grygorii.strashko@ti.com>]

On 08/14/2014 03:12 PM, Alexander Shiyan wrote:
> Thu, 14 Aug 2014 15:13:39 +0300 от Grygorii Strashko <grygorii.strashko@ti.com>:
>> Hi Alexander,
>>
>> On 08/13/2014 07:06 PM, Alexander Shiyan wrote:
>>> Wed, 13 Aug 2014 19:16:22 +0300 от Grygorii Strashko <grygorii.strashko@ti.com>:
>>>> Add Keystone 2 DSP GPIO nodes.
>>>> DSP GPIO banks 0-7 correspond to DSP0-DSP7
>>>>
>>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
>>>> ---
>>>>    arch/arm/boot/dts/k2hk.dtsi |   56 +++++++++++++++++++++++++++++++++++++++++++
>>>>    1 file changed, 56 insertions(+)
>>>>
>>>> diff --git a/arch/arm/boot/dts/k2hk.dtsi b/arch/arm/boot/dts/k2hk.dtsi
>>>> index 321ba2f..009e180 100644
>>>> --- a/arch/arm/boot/dts/k2hk.dtsi
>>>> +++ b/arch/arm/boot/dts/k2hk.dtsi
>>>> @@ -50,5 +50,61 @@
>>>>    			#interrupt-cells = <1>;
>>>>    			ti,syscon-dev = <&devctrl 0x2a0>;
>>>>    		};
>>>> +
>>>> +		dspgpio0: keystone_dsp_gpio@02620240 {
>>>> +			compatible = "ti,keystone-mctrl-gpio";
>>>> +			gpio-controller;
>>>> +			#gpio-cells = <2>;
>>>> +			gpio,syscon-dev = <&devctrl 0x240>;
>>>> +		};
>>>> +
>>>> +		dspgpio1: keystone_dsp_gpio@2620244 {
>>>> +			compatible = "ti,keystone-mctrl-gpio";
>>>> +			gpio-controller;
>>>> +			#gpio-cells = <2>;
>>>> +			gpio,syscon-dev = <&devctrl 0x244>;
>>>> +		};
>>> ...
>>>> +		dspgpio7: keystone_dsp_gpio@262025C {
>>>> +			compatible = "ti,keystone-mctrl-gpio";
>>>> +			gpio-controller;
>>>> +			#gpio-cells = <2>;
>>>> +			gpio,syscon-dev = <&devctrl 0x25c>;
>>>> +		};
>>>
>>> So, devctrl is a syscon device and this DTS introduce several
>>> identical GPIO descriptions?
>>>
>>> On my opinion this should be placed in the gpio-syscon.c,
>>> where you can add support for ti,keystone-dsp0{..7}-gpio.
>>> Such change will avoid parts 2 and 3 of this patch.
>>>
>>> static const struct syscon_gpio_data ti_keystone_dsp0_gpio = {
>>>     .compatible = "ti,keystone-syscon",
>>>     .dat_bit_offset = 0x240 * 8,
>>>     ...
>>>     .set = etc...
>>> };
>>
>> So, if I understand you right, you propose to add 8 additional compatible
>> strings just to encode different register offsets. Is it?
>> 1) add "ti,keystone-mctrl-gpio0"..."ti,keystone-mctrl-gpio7"
> 
> Yes, but replace "mctrl" with "dsp" since mctrl is not applicable here.
> 
>> 2) add 8 structures keystone_mctrl_gpio0..keystone_mctrl_gpio7 in gpio-syscon.c
>>     (which will have only different values of field - .dat_bit_offset = 0x2yy * 8,)
>>
>> 3) add 8 additional items in array syscon_gpio_ids
>> 	{
>> 		.compatible	= "ti,keystone-mctrl-gpio0",
>> 		.data		= &keystone_mctrl_gpio0,
>> 	}, ...
>>
>> I can do it if you strictly insist, BUT I don't like it :(
>> - just imagine how your driver will look look like if 5 or 6 SoCs will re-use it ;)
>> - as I mentioned in cover letter and commit messages even each SoC revision can have
>>    different Syscon implementation with different registers offsets and with different
>>    number of Syscon register ranges (for example for Keystone 2 we already have two
>>    Syscon devices defined in DT).
> 
> The initial version of this driver contains addresses and offsets in, but this approach has
> been criticized by DT maintainers.

Could you provide link on this thread^, pls?

Curious, it looks like Rob Herring has just proposed to encode offsets & bits in DT:
"Re: [PATCH 2/6] leds: add device tree bindings for syscon LEDs"
http://www.spinics.net/lists/arm-kernel/msg354182.html

> 
> "different Syscon with different registers" - is OK, since we use compatible string in definition.
> If you have two identical syscon, just append an unique additional string and use it in this driver.
> 
>> Now we already have 3 Keystone 2 SoC revisions (K2HK, K2L, K2E)  and there are no guarantee
>> that the next revision k2X will have the same register offset for GPIO0.
> 
> Then use more exact string for syscon-gpio, like ti,keystone-k2hk-dsp-gpio0.

Nothing to say :) - DT is funny thing. It has such good feature as phandle, but
people continue hard-coding relation between HW blocks in code :(

Any way, Thanks for your comments. I'll wait a bit then update and resend.


Best regards,
-grygorii
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