Re: [PATCH v2] ARM: dts: i.MX8MM: describe feature controller

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 30.08.22 10:29, Marco Felsch wrote:
> On 22-08-30, Ahmad Fatoum wrote:
>> Hello Marco,
>>
>> On 30.08.22 10:10, Marco Felsch wrote:
>>> Hi Ahamd,
>>>
>>> On 22-08-30, Ahmad Fatoum wrote:
>>>> Now with i.MX8M feature controller driver support available, have the
>>>> OCOTP provide feature control on the i.MX8MM to ensure the kernel DT
>>>> does not cause Linux to access the VPU and its power domains,
>>>> when barebox knows them to be unavailable.
>>>>
>>>> This is needed because the upstream kernel imx8mm.dtsi only
>>>> describes the full-featured SoC, which can lead to hangs when
>>>> instantiating drivers for hardware that's unavailable in a
>>>> less-featureful variant of the SoC.
>>>>
>>>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>>>> ---
>>>> v1 was RFC patch 10/10 of:
>>>> https://lore.barebox.org/barebox/20220818051955.2088238-11-a.fatoum@pengutronix.de/T/#u
>>>>
>>>> Patches 01-08 are still applicable, this replaces the approach in v1
>>>> with a standalone feature controller with having the OCOTP as feature
>>>> controller, like is done for i.MX8MN in patch 08/10 of above referenced
>>>> series.
>>>> ---
>>>>  arch/arm/dts/imx8mm.dtsi | 52 ++++++++++++++++++++++++++++++++++++++++
>>>>  1 file changed, 52 insertions(+)
>>>>
>>>> diff --git a/arch/arm/dts/imx8mm.dtsi b/arch/arm/dts/imx8mm.dtsi
>>>> index cdf212820594..1e81d03d6b84 100644
>>>> --- a/arch/arm/dts/imx8mm.dtsi
>>>> +++ b/arch/arm/dts/imx8mm.dtsi
>>>> @@ -1,10 +1,18 @@
>>>>  // SPDX-License-Identifier: (GPL-2.0+ OR MIT)
>>>> +
>>>> +#include <dt-bindings/features/imx8m.h>
>>>> +
>>>>  / {
>>>>  	aliases {
>>>>  		gpr.reboot_mode = &reboot_mode_gpr;
>>>>  	};
>>>>  };
>>>>  
>>>> +feat: &ocotp {
>>>> +	#feature-cells = <1>;
>>>> +	barebox,feature-controller;
>>>> +};
>>>
>>> Why not just appending the node like:
>>>
>>> / {
>>> 	aliases {
>>> 		gpr.reboot_mode = &reboot_mode_gpr;
>>> 	};
>>>
>>> 	feat: ocotp {
>>> 		#feature-cells = <1>;
>>> 		barebox,feature-controller;
>>> 	};
>>> };
>>
>> Yours adds a new /ocotp node while my patch gives the existing
>> node pointed at by &ocotp an additional label and extends it.
> 
> This should extend the ocotp node as well or would it be a new node
> due to the new label? To me it locked very strange, therefore I asked. I
> never noticed that: "new_label: &old_label {}" is even possible.

It would be a new node, because the ocotp isn't at top level, but
instead at /soc@0/bus@30000000/efuse@30350000. Instead of using the
full path, I used the &ocotp label and instead of using &ocotp everywhere,
I add an additional &feat alias to better convey that the ocotp acts
as a feature controller.

I intend to upstream this and will likely just use the ocotp label
directly then, but having the &feat label here for now allows easily
trying out other providers as mentioned in my previous mail.

Cheers,
Ahmad

> 
> Regards,
>   Marco
> 
>> I prefer the additional label, because it gives us flexibility
>> in future if upstream decides that there should be a dedicated
>> feature controller. In that case we would only need to move
>> the label instead of touching all references. see RFC patch 10/10
>> referenced above.
>>
>> Cheers,
>> Ahmad
>>
>>>
>>> Regards,
>>>   Marco
>>>
>>>> +
>>>>  &pgc_otg1 {
>>>>  	barebox,allow-dummy;
>>>>  };
>>>> @@ -24,3 +32,47 @@
>>>>  		mode-serial = <0x00000010>, <0x40000000>;
>>>>  	};
>>>>  };
>>>> +
>>>> +&A53_1 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_CPU_DUAL>;
>>>> +};
>>>> +
>>>> +&A53_2 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_CPU_QUAD>;
>>>> +};
>>>> +
>>>> +&A53_3 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_CPU_QUAD>;
>>>> +};
>>>> +
>>>> +&gpc {
>>>> +	barebox,feature-gates = <&feat 0>;
>>>> +};
>>>> +
>>>> +&vpu_g1 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> +
>>>> +&vpu_g2 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> +
>>>> +&vpu_blk_ctrl {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> +
>>>> +&pgc_vpumix {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> +
>>>> +&pgc_vpu_g1 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> +
>>>> +&pgc_vpu_g2 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> +
>>>> +&pgc_vpu_h1 {
>>>> +	barebox,feature-gates = <&feat IMX8M_FEAT_VPU>;
>>>> +};
>>>> -- 
>>>> 2.30.2
>>>>
>>>>
>>>>
>>>
>>
>>
>> -- 
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>>
> 


-- 
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