diff mbox series

[RFT,v3,06/27] dt-bindings: timer: arm,arch_timer: Add interrupt-names support

Message ID 20210304213902.83903-7-marcan@marcan.st
State New
Headers show
Series Apple M1 SoC platform bring-up | expand

Commit Message

Hector Martin March 4, 2021, 9:38 p.m. UTC
Not all platforms provide the same set of timers/interrupts, and Linux
only needs one (plus kvm/guest ones); some platforms are working around
this by using dummy fake interrupts. Implementing interrupt-names allows
the devicetree to specify an arbitrary set of available interrupts, so
the timer code can pick the right one.

This also adds the hyp-virt timer/interrupt, which was previously not
expressed in the fixed 4-interrupt form.

Signed-off-by: Hector Martin <marcan@marcan.st>
---
 .../devicetree/bindings/timer/arm,arch_timer.yaml  | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

Comments

Linus Walleij March 5, 2021, 10:18 a.m. UTC | #1
On Thu, Mar 4, 2021 at 10:40 PM Hector Martin <marcan@marcan.st> wrote:

> Not all platforms provide the same set of timers/interrupts, and Linux
> only needs one (plus kvm/guest ones); some platforms are working around
> this by using dummy fake interrupts. Implementing interrupt-names allows
> the devicetree to specify an arbitrary set of available interrupts, so
> the timer code can pick the right one.
>
> This also adds the hyp-virt timer/interrupt, which was previously not
> expressed in the fixed 4-interrupt form.
>
> Signed-off-by: Hector Martin <marcan@marcan.st>

This looks good to me.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij
Marc Zyngier March 8, 2021, 11:12 a.m. UTC | #2
On Thu, 04 Mar 2021 21:38:41 +0000,
Hector Martin <marcan@marcan.st> wrote:
> 

> Not all platforms provide the same set of timers/interrupts, and Linux

> only needs one (plus kvm/guest ones); some platforms are working around

> this by using dummy fake interrupts. Implementing interrupt-names allows

> the devicetree to specify an arbitrary set of available interrupts, so

> the timer code can pick the right one.

> 

> This also adds the hyp-virt timer/interrupt, which was previously not

> expressed in the fixed 4-interrupt form.

> 

> Signed-off-by: Hector Martin <marcan@marcan.st>


Acked-by: Marc Zyngier <maz@kernel.org>


Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
Tony Lindgren March 8, 2021, 5:14 p.m. UTC | #3
* Hector Martin <marcan@marcan.st> [210304 21:40]:
> Not all platforms provide the same set of timers/interrupts, and Linux
> only needs one (plus kvm/guest ones); some platforms are working around
> this by using dummy fake interrupts. Implementing interrupt-names allows
> the devicetree to specify an arbitrary set of available interrupts, so
> the timer code can pick the right one.
> 
> This also adds the hyp-virt timer/interrupt, which was previously not
> expressed in the fixed 4-interrupt form.

I like this one too:

Reviewed-by: Tony Lindgren <tony@atomide.com>
Rob Herring March 9, 2021, 4:11 p.m. UTC | #4
On Mon, Mar 8, 2021 at 3:42 PM Marc Zyngier <maz@kernel.org> wrote:
>
> On Mon, 08 Mar 2021 20:38:41 +0000,
> Rob Herring <robh@kernel.org> wrote:
> >
> > On Fri, Mar 05, 2021 at 06:38:41AM +0900, Hector Martin wrote:
> > > Not all platforms provide the same set of timers/interrupts, and Linux
> > > only needs one (plus kvm/guest ones); some platforms are working around
> > > this by using dummy fake interrupts. Implementing interrupt-names allows
> > > the devicetree to specify an arbitrary set of available interrupts, so
> > > the timer code can pick the right one.
> > >
> > > This also adds the hyp-virt timer/interrupt, which was previously not
> > > expressed in the fixed 4-interrupt form.
> > >
> > > Signed-off-by: Hector Martin <marcan@marcan.st>
> > > ---
> > >  .../devicetree/bindings/timer/arm,arch_timer.yaml  | 14 ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml b/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
> > > index 2c75105c1398..ebe9b0bebe41 100644
> > > --- a/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
> > > +++ b/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
> > > @@ -34,11 +34,25 @@ properties:
> > >                - arm,armv8-timer
> > >
> > >    interrupts:
> > > +    minItems: 1
> > > +    maxItems: 5
> > >      items:
> > >        - description: secure timer irq
> > >        - description: non-secure timer irq
> > >        - description: virtual timer irq
> > >        - description: hypervisor timer irq
> > > +      - description: hypervisor virtual timer irq
> > > +
> > > +  interrupt-names:
> > > +    minItems: 1
> > > +    maxItems: 5
> > > +    items:
> > > +      enum:
> > > +        - phys-secure
> > > +        - phys
> > > +        - virt
> > > +        - hyp-phys
> > > +        - hyp-virt
> >
> > phys-secure and hyp-phys is not very consistent. secure-phys or sec-phys
> > instead?
> >
> > This allows any order which is not ideal (unfortunately json-schema
> > doesn't have a way to define order with optional entries in the middle).
> > How many possible combinations are there which make sense? If that's a
> > reasonable number, I'd rather see them listed out.
>
> The available of interrupts are a function of the number of security
> states, privileged exception levels and architecture revisions, as
> described in D11.1.1:
>
> <quote>
> - An EL1 physical timer.
> - A Non-secure EL2 physical timer.
> - An EL3 physical timer.
> - An EL1 virtual timer.
> - A Non-secure EL2 virtual timer.
> - A Secure EL2 virtual timer.
> - A Secure EL2 physical timer.
> </quote>
>
> * Single security state, EL1 only, ARMv7 & ARMv8.0+ (assumed NS):
>   - physical, virtual
>
> * Single security state, EL1 + EL2, ARMv7 & ARMv8.0 (assumed NS)
>   - physical, virtual, hyp physical
>
> * Single security state, EL1 + EL2, ARMv8.1+ (assumed NS)
>   - physical, virtual, hyp physical, hyp virtual
>
> * Two security states, EL1 + EL3, ARMv7 & ARMv8.0+:
>   - secure physical, physical, virtual
>
> * Two security states, EL1 + EL2 + EL3, ARMv7 & ARMv8.0
>   - secure physical, physical, virtual, hyp physical
>
> * Two security states, EL1 + EL2 + EL3, ARMv8.1+
>   - secure physical, physical, virtual, hyp physical, hyp virtual
>
> * Two security states, EL1 + EL2 + S-EL2 + EL3, ARMv8.4+
>   - secure physical, physical, virtual, hyp physical, hyp virtual,
>     secure hyp physical, secure hyp virtual
>
> Nobody has seen the last combination in the wild (that is, outside of
> a SW model).
>
> I'm really not convinced we want to express this kind of complexity in
> the binding (each of the 7 cases), specially given that we don't
> encode the underlying HW architecture level or number of exception
> levels anywhere, and have ho way to validate such information.

Actually, we can simplify this down to 2 cases:

oneOf:
  - minItems: 2
    items:
      - const: phys
      - const: virt
      - const: hyp-phys
      - const: hyp-virt
  - minItems: 3
    items:
      - const: sec-phys
      - const: phys
      - const: virt
      - const: hyp-phys
      - const: hyp-virt
      - const: sec-hyp-phy
      - const: sec-hyp-virt

And that's below my threshold for not worth the complexity.

Rob
Hector Martin March 9, 2021, 8:28 p.m. UTC | #5
On 10/03/2021 01.11, Rob Herring wrote:
> On Mon, Mar 8, 2021 at 3:42 PM Marc Zyngier <maz@kernel.org> wrote:
>>
>> On Mon, 08 Mar 2021 20:38:41 +0000,
>> Rob Herring <robh@kernel.org> wrote:
>>>
>>> On Fri, Mar 05, 2021 at 06:38:41AM +0900, Hector Martin wrote:
>>>> Not all platforms provide the same set of timers/interrupts, and Linux
>>>> only needs one (plus kvm/guest ones); some platforms are working around
>>>> this by using dummy fake interrupts. Implementing interrupt-names allows
>>>> the devicetree to specify an arbitrary set of available interrupts, so
>>>> the timer code can pick the right one.
>>>>
>>>> This also adds the hyp-virt timer/interrupt, which was previously not
>>>> expressed in the fixed 4-interrupt form.
>>>>
>>>> Signed-off-by: Hector Martin <marcan@marcan.st>
>>>> ---
>>>>   .../devicetree/bindings/timer/arm,arch_timer.yaml  | 14 ++++++++++++++
>>>>   1 file changed, 14 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml b/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
>>>> index 2c75105c1398..ebe9b0bebe41 100644
>>>> --- a/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
>>>> +++ b/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
>>>> @@ -34,11 +34,25 @@ properties:
>>>>                 - arm,armv8-timer
>>>>
>>>>     interrupts:
>>>> +    minItems: 1
>>>> +    maxItems: 5
>>>>       items:
>>>>         - description: secure timer irq
>>>>         - description: non-secure timer irq
>>>>         - description: virtual timer irq
>>>>         - description: hypervisor timer irq
>>>> +      - description: hypervisor virtual timer irq
>>>> +
>>>> +  interrupt-names:
>>>> +    minItems: 1
>>>> +    maxItems: 5
>>>> +    items:
>>>> +      enum:
>>>> +        - phys-secure
>>>> +        - phys
>>>> +        - virt
>>>> +        - hyp-phys
>>>> +        - hyp-virt
>>>
>>> phys-secure and hyp-phys is not very consistent. secure-phys or sec-phys
>>> instead?
>>>
>>> This allows any order which is not ideal (unfortunately json-schema
>>> doesn't have a way to define order with optional entries in the middle).
>>> How many possible combinations are there which make sense? If that's a
>>> reasonable number, I'd rather see them listed out.
>>
>> The available of interrupts are a function of the number of security
>> states, privileged exception levels and architecture revisions, as
>> described in D11.1.1:
>>
>> <quote>
>> - An EL1 physical timer.
>> - A Non-secure EL2 physical timer.
>> - An EL3 physical timer.
>> - An EL1 virtual timer.
>> - A Non-secure EL2 virtual timer.
>> - A Secure EL2 virtual timer.
>> - A Secure EL2 physical timer.
>> </quote>
>>
>> * Single security state, EL1 only, ARMv7 & ARMv8.0+ (assumed NS):
>>    - physical, virtual
>>
>> * Single security state, EL1 + EL2, ARMv7 & ARMv8.0 (assumed NS)
>>    - physical, virtual, hyp physical
>>
>> * Single security state, EL1 + EL2, ARMv8.1+ (assumed NS)
>>    - physical, virtual, hyp physical, hyp virtual
>>
>> * Two security states, EL1 + EL3, ARMv7 & ARMv8.0+:
>>    - secure physical, physical, virtual
>>
>> * Two security states, EL1 + EL2 + EL3, ARMv7 & ARMv8.0
>>    - secure physical, physical, virtual, hyp physical
>>
>> * Two security states, EL1 + EL2 + EL3, ARMv8.1+
>>    - secure physical, physical, virtual, hyp physical, hyp virtual
>>
>> * Two security states, EL1 + EL2 + S-EL2 + EL3, ARMv8.4+
>>    - secure physical, physical, virtual, hyp physical, hyp virtual,
>>      secure hyp physical, secure hyp virtual
>>
>> Nobody has seen the last combination in the wild (that is, outside of
>> a SW model).
>>
>> I'm really not convinced we want to express this kind of complexity in
>> the binding (each of the 7 cases), specially given that we don't
>> encode the underlying HW architecture level or number of exception
>> levels anywhere, and have ho way to validate such information.
> 
> Actually, we can simplify this down to 2 cases:
> 
> oneOf:
>    - minItems: 2
>      items:
>        - const: phys
>        - const: virt
>        - const: hyp-phys
>        - const: hyp-virt
>    - minItems: 3
>      items:
>        - const: sec-phys
>        - const: phys
>        - const: virt
>        - const: hyp-phys
>        - const: hyp-virt
>        - const: sec-hyp-phy
>        - const: sec-hyp-virt
> 
> And that's below my threshold for not worth the complexity.

This makes sense. Since we aren't using the sec-hyp stuff here, and 
those go at the end of the list, we can omit them from this patch for 
now and add them whenever they're needed for a platform. Does that sound OK?
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml b/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
index 2c75105c1398..ebe9b0bebe41 100644
--- a/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
+++ b/Documentation/devicetree/bindings/timer/arm,arch_timer.yaml
@@ -34,11 +34,25 @@  properties:
               - arm,armv8-timer
 
   interrupts:
+    minItems: 1
+    maxItems: 5
     items:
       - description: secure timer irq
       - description: non-secure timer irq
       - description: virtual timer irq
       - description: hypervisor timer irq
+      - description: hypervisor virtual timer irq
+
+  interrupt-names:
+    minItems: 1
+    maxItems: 5
+    items:
+      enum:
+        - phys-secure
+        - phys
+        - virt
+        - hyp-phys
+        - hyp-virt
 
   clock-frequency:
     description: The frequency of the main counter, in Hz. Should be present