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

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 +--- +$id: http://devicetree.org/schemas/mailbox/mediatek,gce-props.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml#

+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...

I'd set that to a more sensible value of 32 - eventually we can extend it later, if ever needed.

Besides, nice job about all this documentation of the GCE and its events: love it!

Cheers, Angelo