Re: [PATCH] dt-bindings: mailbox: mtk-gce: Convert txt to json-schema

[AngeloGioacchino Del Regno]

Il 20/05/22 10:15, Krzysztof Kozlowski ha scritto:
> On 19/05/2022 12:18, AngeloGioacchino Del Regno wrote:
> > Convert the mtk-gce documentation from freeform text format to a
> > json-schema.
> >
> > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
> > ---
> >   .../bindings/mailbox/mediatek,gce-mbox.yaml   | 114 ++++++++++++++++++
> >   .../devicetree/bindings/mailbox/mtk-gce.txt   |  82 -------------
> >   2 files changed, 114 insertions(+), 82 deletions(-)
> >   create mode 100644 Documentation/devicetree/bindings/mailbox/mediatek,gce-mbox.yaml
> >   delete mode 100644 Documentation/devicetree/bindings/mailbox/mtk-gce.txt
> >
> > diff --git a/Documentation/devicetree/bindings/mailbox/mediatek,gce-mbox.yaml b/Documentation/devicetree/bindings/mailbox/mediatek,gce-mbox.yaml
> > new file mode 100644
> > index 000000000000..750391b4038c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mailbox/mediatek,gce-mbox.yaml
> > @@ -0,0 +1,114 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/mailbox/mediatek,gce-mbox.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: MediaTek Global Command Engine (GCE) mailbox
> > +
> > +maintainers:
> > +  - Houlong Wei <houlong.wei@xxxxxxxxxxxx>
> > +
> > +description: |
> > +  The Global Command Engine (GCE) is used to help read/write registers
> > +  with critical time limitation, such as updating display configuration
> > +  during the vblank.
> > +  The GCE can be used to implement the Command Queue (CMDQ) driver.
>
> Mention the headers in description.

  Values for properties used by the GCE, such as sub-system IDs, thread

  priority and event IDs are defined in 'dt-bindings/gce/<chip>-gce.h'.

Would that be enough, or should I list all of the headers?

> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - mediatek,mt6779-gce
> > +      - mediatek,mt8173-gce
> > +      - mediatek,mt8183-gce
> > +      - mediatek,mt8186-gce
> > +      - mediatek,mt8192-gce
> > +      - mediatek,mt8195-gce
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  clocks:
> > +    maxItems: 1
> > +
> > +  clock-names:
> > +    items:
> > +      - const: gce
> > +
> > +  '#mbox-cells':
> > +    description: |
> > +      The first cell describes the mailbox channel, which is the GCE Thread ID;
> > +      The second cell describes the priority of the GCE thread.
> > +    const: 2
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - interrupts
> > +  - clocks
> > +  - clock-names
> > +  - '#mbox-cells'
> > +
> > +additionalProperties: false
> > +
> > +allOf:
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          enum:
> > +            - mediatek,mt8195-gce
> > +    then:
> > +      properties:
> > +        clocks:
> > +          maxItems: 2
>
> Are you sure this works on mt8195-gce?

Thanks for that, I've just rechecked the driver and.. no, that won't
work for MT8195: it's just one clock there (like the others) and the
clock names aren't even enforced, as the driver is always taking the
clock at index 0.

I got confused because the driver uses a slightly different kind of
logic when probing on SoCs with multiple mailboxes, specifically:
 - For single mailbox, having a clock with name "gce" is enforced
   as it's grabbing it with devm_clk_get(dev, clk_name), where the
   clock name is declared in a string called "clk_name";
 - For multiple mailboxes, it's looking for an of_alias, declared
   in an array of strings called "clk_names" and getting the clock
   with of_clk_get(node, 0).


So there comes my confusion, recapping:

static const char * const clk_name = "gce";
                 <- this is a clock name
static const char * const clk_names[] = { "gce0", "gce1" }; <- OF alias names


At this point, I think that the best idea would be to fix this issue
first... luckily there's no MT8195 devicetree upstream yet, so I would
technically not be breaking any ABI by changing it to be the same as
the others.

Easier explanation: plan is to change the driver such that we won't
need anything different from the others in this schema.

New version coming soon, then....

Regards,
Angelo