On 13 October 2017 at 19:50, Rob Herring <robh+dt@xxxxxxxxxx> wrote:
> On Fri, Oct 13, 2017 at 4:47 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>> [+Mark]
>>
>> On 12/10/17 23:24, Ard Biesheuvel wrote:
>>> On 12 October 2017 at 22:34, Rob Herring <robh+dt@xxxxxxxxxx> wrote:
>>>> On Thu, Oct 12, 2017 at 1:32 PM, Ard Biesheuvel
>>>> <ard.biesheuvel@xxxxxxxxxx> wrote:
>>>>> The Socionext Synquacer SoC's implementation of GICv3 has a so-called
>>>>> 'pre-ITS', which maps 32-bit writes targeted at a separate window of
>>>>> size '4 << device_id_bits' onto writes to GITS_TRANSLATER with device
>>>>> ID taken from bits [device_id_bits + 1:2] of the window offset.
>>>>> Writes that target GITS_TRANSLATER directly are reported as originating
>>>>> from device ID #0.
>>>>>
>>>>> So add a workaround for this. Given that this breaks isolation, clear
>>>>> the IRQ_DOMAIN_FLAG_MSI_REMAP flag as well.
>>>>>
>>>>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>>>>> ---
>>>>> Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt | 4 ++
>>>>> arch/arm64/Kconfig | 8 +++
>>>>> drivers/irqchip/irq-gic-v3-its.c | 63 +++++++++++++++++++-
>>>>> 3 files changed, 72 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
>>>>> index 4c29cdab0ea5..0798a61bbf99 100644
>>>>> --- a/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
>>>>> +++ b/Documentation/devicetree/bindings/interrupt-controller/arm,gic-v3.txt
>>>>> @@ -75,6 +75,10 @@ These nodes must have the following properties:
>>>>> - reg: Specifies the base physical address and size of the ITS
>>>>> registers.
>>>>>
>>>>> +Optional:
>>>>> +- socionext,synquacer-pre-its: (u32, u32) tuple describing the host address
>>>>> + and size of the pre-ITS window, as implemented on the Socionext Synquacer SoC
>>>>
>>>> Sounds like a separate h/w block to me and addresses should be in
>>>> "reg". I would suggest you define a separate node for the pre-its
>>>> block and then use of_find_compatible_node() from the GIC driver to
>>>> retrieve the node and whatever you need from it. Or do an SoC specific
>>>> compatible string for the GIC and let that imply whatever information
>>>> you need. Then the next quirk doesn't need a DT update.
>>>>
>>>
>>> For my understanding, you mean either
>>>
>>> gic: interrupt-controller@30000000 {
>>> compatible = "arm,gic-v3";
>>> ...
>>>
>>> its: gic-its@30020000 {
>>> compatible = "arm,gic-v3-its";
>>> reg = <0x0 0x30020000 0x0 0x20000>;
>>> #msi-cells = <1>;
>>> msi-controller;
>>> };
>>> };
>>>
>>> preits@58000000 {
>>> compatible = "socionext,synquacer-pre-its";
>>> reg = <0x0 0x58000000 0x0 0x200000>;
>>> msi-slave = <&its>;
>>> };
>>>
>>> or
>>>
>>> gic: interrupt-controller@30000000 {
>>> compatible = "arm,gic-v3";
>>> ...
>>>
>>> its: gic-its@30020000 {
>>> compatible = "socionext,synquacer-pre-its", "arm,gic-v3-its";
>>> reg = <0x0 0x30020000 0x0 0x20000>,
>>> <0x0 0x58000000 0x0 0x200000>;
>>> #msi-cells = <1>;
>>> msi-controller;
>>> };
>>> };
>>>
>>> right?
>>>
>>> Marc, what do you think? IIRC we did discuss option #2 at some point,
>>> but I don't remember if/why we rejected it.
>>
>> I dislike #2 because these registers are not part of the regular ITS,
>> and would get in the way of potential extensions of the ITS (I don't
>> know of any, but just in case...).
>>
>> I also dislike #1 as the "msi-slave" part is both ugly and confusing
>> (are we writing to the ITS? to the pre-ITS?).
>
> Why do you need this? Are you ever going to have multiple pre-its's?
The question is really whether we are ever going to have multiple
ITSes, in which case we will need to identify which ITS this single
pre-ITS is associated with, given that it can only target one. And
while I would prefer zero pre-ITSes in all cases [as would Marc, I'm
sure], having a pre-ITS for each ITS frame is not unimaginable either.
So yes, we need to record this information in one way or the other.
> That's why I suggested just using of_find_compatible_node().
>
>> How about putting the pre-its node *inside* the its node itself? It
>> makes it obvious which pre-ITS corresponds to which ITS, and it leaves
>> the ITS regs untouched.
>
> Not wild about this, but it's fine if you do need to handle multiple instances.
>
> Rob
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