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

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

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.

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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