Re: [PATCH v9 15/15] irqchip: mbigen: Add ACPI support

[Hanjun Guo <hanjun.guo@linaro.org>]

Hi Al,

Thanks for your feedback, reply inline.

On 03/28/2017 02:56 AM, Al Stone wrote:
> On 03/27/2017 09:27 AM, Lorenzo Pieralisi wrote:
>> [+Al,Darren to comment on _DSD review process]
>>
>> On Mon, Mar 27, 2017 at 12:24:45PM +0000, Gabriele Paoloni wrote:
>>> Hi Marc Many thanks for your comments
>>>> Hanjun, John,
>>>>
>>>> On 22/03/17 14:12, John Garry wrote:
>>>>> On 21/03/2017 14:45, Lorenzo Pieralisi wrote:
>>>>>> On Tue, Mar 07, 2017 at 08:40:10PM +0800, Hanjun Guo wrote:
>>>>>>> From: Hanjun Guo <hanjun.guo@linaro.org>
>>>>>>>
>>>>>>> With the preparation of platform msi support and interrupt producer
>>>>>>> in DSDT, we can add mbigen ACPI support now.
>>>>>>>
>>>>>>> We are using Interrupt resource type in _CRS methd to indicate
>>>> number
>>>>>>> of irq pins instead of num_pins in DT to avoid _DSD usage in this
>>>> case.
>>>>>>>
>>>>>>> For mbigen,
>>>>>>>      Device(MBI0) {
>>>>>>>            Name(_HID, "HISI0152")
>>>>>>>            Name(_UID, Zero)
>>>>>>>            Name(_CRS, ResourceTemplate() {
>>>>>>>                    Memory32Fixed(ReadWrite, 0xa0080000, 0x10000)
>>>>>>> 		  Interrupt(ResourceProducer,...) {12,14,....}
>>>>>>
>>>>>> What do these interrupt numbers represent ? This looks wrong to me.
>>>>>> An interrupt descriptor is there to describe the interrupts a device
>>>>>> can generate; you are using it just to add a "standard" (that is
>>>>>> not standard at all) way of counting the number of vectors allocated
>>>>>> to this specific chip and that's just wrong.
>>>>>>
>>>>>
>>>>> As I understand, the count of interrupts we are declaring for the
>>>> mbigen
>>>>> is the same as the sum of interrupts for that mbigen's children.
>>>>>
>>>>> So at the point we probe the mbigen, can we just deference the
>>>> children
>>>>> to count their interrupts, and use this as the #msis?
>>>>>
>>>>>> Can't you use something like Agustin did in the QCOM combiner:
>>>>>>
>>>>>> drivers/irqchip/qcom-irq-combiner.c
>>>>>>
>>>>>> to detect the MSI vector length (ie by describing the MBIgen through
>>>>>> generic registers and use the bit width to compute the vector
>>>>>> lenght) ? I am not sure how feasible it is given that my knowledge
>>>>>> of MBIgen is pretty poor.
>>>>>>
>>>>>> I understand we want to avoid _DSD properties but we should not
>>>>>> work around standard bindings to achieve that goal.
>>>>>>
>>>>>
>>>>> We use "num-pins" for dt solution, but it is not so welcome here.
>>>>
>>>> Well, this device is already completely out of any standard description
>>>> on the ACPI side. And given that it bloats both the ACPI tables and the
>>>> kernel data structures, I can only suggest that you take advantage of
>>>> _DSD here, as misusing the standard properties is not something that we
>>>> should condone. It will also make the driver more manageable, as it
>>>> will
>>>> use similar properties on both firmware implementations.
>>>>
>>>> I feel like I need to stress the urgency here. We're at -rc4, and still
>>>> with unsolved issues. None of us want to miss the next merge window.
>>>>
>>>
>>> As follow up our guys would work on a solution whose ACPI table looks
>>> like the following one:
>>>
>>> For mbigen,
>>>      Device(MBI0) {
>>>            Name(_HID, "HISI0152")
>>>            Name(_UID, Zero)
>>>            Name(_CRS, ResourceTemplate() {
>>>                    Memory32Fixed(ReadWrite, 0xa0080000, 0x10000)
>>>            })
>>>
>>>      Name(_DSD, Package () {
>>>        ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>>>        Package ()
>>>        {
>>>          Package () {"num-pins", xxx}
>>>        }
>>>      })
>>>      }
>
> Please fix the indentation here; the ASL parser doesn't care, but I don't
> see '}'s as clearly as it does :).  In particular, _DSD usage *must* be for
> a device and it does not look like that if one doesn't carefully count all
> the parentheses and braces.

I will fix it :)

>
>>>
>>> For devices,
>>>     Device(COM0) {
>>>            Name(_HID, "ACPIIDxx")
>>>            Name(_UID, Zero)
>>>            Name(_CRS, ResourceTemplate() {
>>>                   Memory32Fixed(ReadWrite, 0xb0030000, 0x10000)
>>> 		 Interrupt(ResourceConsumer,..., "\_SB.MBI0") {12}
>>>            })
>>>      }
>>>
>>>
>>> Marc, Lorenzo if you are ok with the above we will submit v10 based on this...
>>
>> I am ok with it. I am not 100% up-to-date on what's the status on _DSD
>> bindings/review/guidelines but it would be certainly a good idea to
>> kickstart the process for MBIgen which basically means following this
>> as far as I know (and post to the relevant mailing list):
>>
>> https://github.com/ahs3/dsd/blob/master/documentation/process_rules.txt
>
> So, let's correct this bit: consider that URL deprecated, please, and refer
> instead to the text that was agreed upon and in the kernel tree:
>
> 	Documentation/acpi/DSD-properties-rules.txt
>
>> Al and Darren may add to that as they have more insights.
>
> Since this use of _DSD is very specific to this device, and this device
> only, I don't have any real objections.

Thanks for the confirmation.

> I will say that "num-pins" is
> not terribly descriptive so it would be really good to either use a much
> more descriptive name or add plenty of commentary in the code -- and
> preferably both.  I would recommend including the ASL in the code comments,
> with a description of how the property is to be used and what it means.

"num-pins" is used for mbigen DT support:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/interrupt-controller/hisilicon,mbigen-v2.txt

I think we can use the name unchanged and adding more comments
as you suggested, will cc you for this updated patch.

Thanks
Hanjun