linux-kernel - Re: [PATCH 6/6] i2c: designware: Use PCI PSP driver for communication

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Message-ID: <ba2ce999-5cc2-be73-6212-a5db903b294f@amd.com>
Date:   Thu, 16 Feb 2023 15:27:35 -0600
From:   "Limonciello, Mario" <mario.limonciello@....com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
        Jan Dąbroś <jsd@...ihalf.com>,
        Grzegorz Bernacki <gjb@...ihalf.com>,
        Thomas Rijo-john <Rijo-john.Thomas@....com>,
        Lendacky Thomas <Thomas.Lendacky@....com>,
        herbert@...dor.apana.org.au,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-i2c@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] i2c: designware: Use PCI PSP driver for communication

On 2/16/2023 15:16, Andy Shevchenko wrote:
> On Thu, Feb 16, 2023 at 03:01:35PM -0600, Limonciello, Mario wrote:
>> On 2/16/2023 14:59, Andy Shevchenko wrote:
>>> On Thu, Feb 16, 2023 at 02:55:07PM -0600, Limonciello, Mario wrote:
>>>> On 2/16/2023 08:56, Andy Shevchenko wrote:
>>>>> On Thu, Feb 16, 2023 at 07:29:53AM -0600, Mario Limonciello wrote:
>>>>>> On 2/16/23 07:27, Jarkko Nikula wrote:
>>>>>>> On 2/10/23 00:38, Mario Limonciello wrote:
> 
> ...
> 
>>>>>>>>        config I2C_DESIGNWARE_AMDPSP
>>>>>>>>          bool "AMD PSP I2C semaphore support"
>>>>>>>> -    depends on X86_MSR
>>>>>>>>          depends on ACPI
>>>>>>>>          depends on I2C_DESIGNWARE_PLATFORM
>>>>>>>> +    depends on CRYPTO_DEV_SP_PSP && !(I2C_DESIGNWARE_PLATFORM=y &&
>>>>>>>> CRYPTO_DEV_CCP_DD=m)
>>>>>>>>          help
>>>>>>>
>>>>>>> Would this look better if split? I.e.
>>>>>>>
>>>>>>>        depends on CRYPTO_DEV_SP_PSP
>>>>>>>        depends on !(I2C_DESIGNWARE_PLATFORM=y && CRYPTO_DEV_CCP_DD=m)
>>>>>> Yes, thanks I'll change that for next version.
>>>>>
>>>>> I'm wondering if this is homegrown implementation of 'imply' keyword?
>>>>
>>>> Like this?
>>>>
>>>> config I2C_DESIGNWARE_AMDPSP
>>>>      depends on CRYPTO_DEV_SP_PSP
>>>>      depends on CRYPTO_DEV_CCP_DD
>>>>
>>>> config CRYPTO_DEV_CCP_DD
>>>>      imply I2C_DESIGNWARE_PLATFORM
>>>
>>> Looks okay, but I'm not familiar with this code. The documentation about
>>> 'imply' can be found here:
>>>
>>> https://www.kernel.org/doc/html/latest/kbuild/kconfig-language.html#menu-attributes
>>
>> Yeah I found that, but this was my first time using imply, so I was hoping
>> someone who has used it could validate I interpreted it correctly.
>>
>> Following the example CRYPTO_DEV_CCP_DD would be FOO and
>> I2C_DESIGNWARE_PLATFORM would be BAZ so I thought so.
> 
> 'imply' == weak 'select', it means that the target option may or may not be
> selected. I.o.w. "optional" dependency.
> 
> Does CRYPTO_DEV_CCP_DD use I2C DesignWare code?
> 
> If I understand correctly the "depends on !(I2C_DESIGNWARE_PLATFORM=y &&
> CRYPTO_DEV_CCP_DD=m)" you want to have IS_REACHABLE() in your code and actually
> "imply CRYPTO_DEV_CCP_DD" in the I2C_DESIGNWARE_AMDPSP.
> 
> 

Allowing that combination and using IS_REACHABLE means that it's going 
to actually load earlier that expected, so I suppose it needs to be 
something like this then in the probe code for i2c-designware-amdpsp.c:

if (!IS_REACHABLE()
	return -EPROBE_DEFER;

Right?