Re: [PATCH v3 1/3] dt-bindings: mailbox: Add mediatek,gce-props.yaml

["Jason-JH Lin (林睿祥)" <Jason-JH.Lin@mediatek.com>]

Hi Angelo,

Thanks for the reviews.

On Fri, 2024-01-19 at 11:53 +0100, AngeloGioacchino Del Regno wrote:
> Il 19/01/24 07:32, Jason-JH.Lin ha scritto:
> > Add mediatek,gce-props.yaml for common GCE properties that is used
> > for
> > both mailbox providers and consumers. We place the common property
> > "mediatek,gce-events" in this binding currently.
> > 
> > The property "mediatek,gce-events" is used for GCE event ID
> > corresponding
> > to a hardware event signal sent by the hardware or a sofware
> > driver.
> > If the mailbox providers or consumers want to manipulate the value
> > of
> > the event ID, they need to know the specific event ID.
> > 
> > Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
> > ---
> >   .../bindings/mailbox/mediatek,gce-props.yaml  | 52
> > +++++++++++++++++++
> >   1 file changed, 52 insertions(+)
> >   create mode 100644
> > Documentation/devicetree/bindings/mailbox/mediatek,gce-props.yaml
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/mailbox/mediatek,gce-props.yaml 
> > b/Documentation/devicetree/bindings/mailbox/mediatek,gce-props.yaml
> > new file mode 100644
> > index 000000000000..68b519ff089f
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/mailbox/mediatek,gce-
> > props.yaml
> > @@ -0,0 +1,52 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: 
> > https://urldefense.com/v3/__http://devicetree.org/schemas/mailbox/mediatek,gce-props.yaml*__;Iw!!CTRNKA9wMg0ARbw!kMCkhwQ_az8HouSQgqMuDC5QpKFizQrWMlwaWPfYp1GphlueXVfPfS9FA83806_7K_qqcfHOaprqAWNOoBkzsTJNUSZpugRS_Q$
> >  
> > +$schema: 
> > https://urldefense.com/v3/__http://devicetree.org/meta-schemas/core.yaml*__;Iw!!CTRNKA9wMg0ARbw!kMCkhwQ_az8HouSQgqMuDC5QpKFizQrWMlwaWPfYp1GphlueXVfPfS9FA83806_7K_qqcfHOaprqAWNOoBkzsTJNUSYsot_sog$
> >  
> > +
> > +title: MediaTek Global Command Engine Common Propertes
> > +
> > +maintainers:
> > +  - Houlong Wei <houlong.wei@mediatek.com>
> > +
> > +description:
> > +  The Global Command Engine (GCE) is an instruction based, multi-
> > threaded,
> > +  single-core command dispatcher for MediaTek hardware. The
> > Command Queue
> > +  (CMDQ) mailbox driver is a driver for GCE, implemented using the
> > Linux
> > +  mailbox framework. It is used to receive messages from mailbox
> > consumers
> > +  and configure GCE to execute the specified instruction set in
> > the message.
> > +  We use mediatek,gce-mailbox.yaml to define the properties for
> > CMDQ mailbox
> > +  driver. A device driver that uses the CMDQ driver to configure
> > its hardware
> > +  registers is a mailbox consumer. The mailbox consumer can
> > request a mailbox
> > +  channel corresponding to a GCE hardware thread to send a
> > message, specifying
> > +  that the GCE thread to configure its hardware. The mailbox
> > provider can also
> > +  reserved a mailbox channel to configure GCE hardware register by
> > the spcific
> > +  GCE thread. This binding defines the common GCE properties for
> > both mailbox
> > +  provider and consumers.
> > +
> > +properties:
> > +  mediatek,gce-events:
> > +    description:
> > +      GCE has an event table in SRAM, consisting of 1024 event IDs
> > (0~1023).
> > +      Each event ID has a boolean event value with the default
> > value 0.
> > +      The property mediatek,gce-events is used to obtain the event
> > IDs.
> > +      Some gce-events are hardware-bound and cannot be changed by
> > software.
> > +      For instance, in MT8195, when VDO0_MUTEX is stream done,
> > VDO_MUTEX will
> > +      send an event signal to GCE, setting the value of event ID
> > 597 to 1.
> > +      Similarly, in MT8188, the value of event ID 574 will be set
> > to 1 when
> > +      VOD0_MUTEX is stream done.
> > +      On the other hand, some gce-events are not hardware-bound
> > and can be
> > +      changed by software. For example, in MT8188, we can set the
> > value of
> > +      event ID 855, which is not bound to any hardware, to 1 when
> > the driver
> > +      in the secure world completes a task. However, in MT8195,
> > event ID 855
> > +      is already bound to VDEC_LAT1, so we need to select another
> > event ID to
> > +      achieve the same purpose. This event ID can be any ID that
> > is not bound
> > +      to any hardware and is not yet used in any software driver.
> > +      To determine if the event ID is bound to the hardware or
> > used by a
> > +      software driver, refer to the GCE header
> > +      include/dt-bindings/gce/<chip>-gce.h of each chip.
> > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > +    minItems: 1
> > +    maxItems: 1024
> 
> maxItems: 1024 seems to be a bit too many... this means that one
> devicetree node
> may have up to 1024 gce events, which is impossible! If a driver
> needed all of
> the 1024 events, this means that it's not an user of the GCE, but the
> GCE itself!
> 
> Imagine seeing a devicetree node with 1024 array entries for
> mediatek,gce-events...
> 
Yes, that's impossible to set up to 1024 array entries.
I just have used the maximum value to cover all the possible cases.

> I'd set that to a more sensible value of 32 - eventually we can
> extend it later,
> if ever needed.
> 
OK, I agree with that!
I'll change the maxItems to 32.

> Besides, nice job about all this documentation of the GCE and its
> events: love it!
> 
I'm appreciate you love it :)

Regards,
Jason-JH.Lin

> Cheers,
> Angelo
> 
> 
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