linux-kernel - Re: [PATCH v4] cdx: add MSI support for CDX bus

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Message-ID: <99d707a3-5274-1603-d0ed-f67ce83b7e29@amd.com>
Date:   Thu, 5 Oct 2023 20:35:28 +0530
From:   "Gupta, Nipun" <nipun.gupta@....com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>, maz@...nel.org, jgg@...pe.ca,
        linux-kernel@...r.kernel.org, git@....com, harpreet.anand@....com,
        pieter.jansen-van-vuuren@....com, nikhil.agarwal@....com,
        michal.simek@....com, abhijit.gangurde@....com,
        srivatsa@...il.mit.edu
Subject: Re: [PATCH v4] cdx: add MSI support for CDX bus



On 10/5/2023 8:24 PM, Greg KH wrote:
> On Thu, Oct 05, 2023 at 08:07:35PM +0530, Gupta, Nipun wrote:
>> Hi Greg,
>>
>> On 10/5/2023 7:30 PM, Greg KH wrote:
>>> On Thu, Oct 05, 2023 at 03:46:34PM +0200, Thomas Gleixner wrote:
>>>> On Thu, Oct 05 2023 at 12:24, Greg KH wrote:
>>>>>> diff --git a/drivers/cdx/Kconfig b/drivers/cdx/Kconfig
>>>>>> index a08958485e31..86df7ccb76bb 100644
>>>>>> --- a/drivers/cdx/Kconfig
>>>>>> +++ b/drivers/cdx/Kconfig
>>>>>> @@ -8,6 +8,7 @@
>>>>>>    config CDX_BUS
>>>>>>    	bool "CDX Bus driver"
>>>>>>    	depends on OF && ARM64
>>>>>> +	select GENERIC_MSI_IRQ_DOMAIN
>>>>>
>>>>> This config option isn't in my tree anywhere, where did it come from?
>>>>> What is it supposed to do?
>>>>
>>>> 13e7accb81d6 ("genirq: Get rid of GENERIC_MSI_IRQ_DOMAIN") :)
>>>
>>> Ok, so this hasn't been tested since the 6.2 release?  Wow, I think
>>> someone from AMD needs to take a deep look at this and verify that it
>>> actually is doing what it is supposed to be doing...
>>
>> The patch Thomas mentioned renames "GENERIC_MSI_IRQ_DOMAIN" to
>> "GENERIC_MSI_IRQ"; and in our testing "GENERIC_MSI_IRQ" is also selected as
>> 'ARM64' is enabled which enables 'ARM_GIC_V3_ITS' which in-turn selects
>> 'GENERIC_MSI_IRQ'.
> 
> Ok, but that's not what this patch "selects" at all :(

"GENERIC_MSI_IRQ" gets enabled because of enabling "ARM64", and you are 
right that what we are selecting here does not have any meaning now 
(after 6.2).

> 
>> The patch is tested for MSI functionality on 6.6-rc1. We will re-look into
>> the config dependencies to avoid such issues, but please be assured that the
>> patch has been validated.
> 
> How has the dependancy been validated as correct if there is no such
> thing in this kernel?

Apology for the confusion. By validated I meant tested for MSI 
functionality in CDX. Agree that "select GENERIC_MSI_IRQ_DOMAIN" needs 
to be fixed here. Will update in next spin. :)

Thanks,
Nipun

> 
> confused,
> 
> greg k-h