linux-kernel - Re: [PATCH v22 1/4] dt-bindings: soc: Add documentation for the MediaTek GCE unit

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Date:   Mon, 2 Jul 2018 20:30:40 -0600
From:   Rob Herring <robh@...nel.org>
To:     Houlong Wei <houlong.wei@...iatek.com>
Cc:     Jassi Brar <jassisinghbrar@...il.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Daniel Kurtz <djkurtz@...omium.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        Sascha Hauer <kernel@...gutronix.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Nicolas Boichat <drinkcat@...omium.org>,
        CK HU <ck.hu@...iatek.com>,
        Bibby Hsieh <bibby.hsieh@...iatek.com>,
        YT Shen <yt.shen@...iatek.com>,
        Daoyuan Huang <daoyuan.huang@...iatek.com>,
        Jiaguang Zhang <jiaguang.zhang@...iatek.com>,
        Dennis-YC Hsieh <dennis-yc.hsieh@...iatek.com>,
        Monica Wang <monica.wang@...iatek.com>,
        HS Liao <hs.liao@...iatek.com>, ginny.chen@...iatek.com,
        enzhu.wang@...iatek.com
Subject: Re: [PATCH v22 1/4] dt-bindings: soc: Add documentation for the
 MediaTek GCE unit

On Wed, Jun 27, 2018 at 07:16:09PM +0800, Houlong Wei wrote:
> This adds documentation for the MediaTek Global Command Engine (GCE) unit
> found in MT8173 SoCs.
> 
> Signed-off-by: Houlong Wei <houlong.wei@...iatek.com>
> Signed-off-by: HS Liao <hs.liao@...iatek.com>
> ---
> Hi Rob,
>   I don't add your ACK in this version since the dt-binding description
> has been changed. Thanks.
> ---
>  .../devicetree/bindings/mailbox/mtk-gce.txt        |   65 ++++++++++++++++++++
>  include/dt-bindings/gce/mt8173-gce.h               |   48 +++++++++++++++
>  2 files changed, 113 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/mtk-gce.txt
>  create mode 100644 include/dt-bindings/gce/mt8173-gce.h
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/mtk-gce.txt b/Documentation/devicetree/bindings/mailbox/mtk-gce.txt
> new file mode 100644
> index 0000000..26f65a4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/mtk-gce.txt
> @@ -0,0 +1,65 @@
> +MediaTek GCE
> +===============
> +
> +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.
> +
> +CMDQ driver uses mailbox framework for communication. Please refer to
> +mailbox.txt for generic information about mailbox device-tree bindings.
> +
> +Required properties:
> +- compatible: Must be "mediatek,mt8173-gce"
> +- reg: Address range of the GCE unit
> +- interrupts: The interrupt signal from the GCE block
> +- clock: Clocks according to the common clock binding
> +- clock-names: Must be "gce" to stand for GCE clock
> +- thread-num: Maximum threads count of GCE.

mediatek,thread-num

Is this needed for anything other than error checking the thread id in 
the mbox cells? if that's it, then drop it. 

> +- #mbox-cells: Should be 4.
> +	<&phandle channel timeout priority atomic_exec>
> +	phandle: Label name of a gce node.
> +	channel: Channel of mailbox. Be equal to the thread id of GCE.
> +	timeout: Maximum time of software waiting GCE processing done, in unit
> +		of millisecond.
> +	priority: Priority of GCE thread.
> +	atomic_exec: GCE processing continuous packets of commands in atomic
> +		way.
> +
> +Required properties for a client device:
> +- mboxes: Client use mailbox to communicate with GCE, it should have this
> +  property and list of phandle, mailbox specifiers.
> +- gce-subsys: Specify the sub-system id which is corresponding to the register
> +  address.

What is this for?

> +
> +Optional properties for a client device:
> +- gce-event: Specify the event if the client has any. Because the event is
> +  parsed by client, so client can replace 'gce-event' with other meaningful
> +  name.

If the client sets the name, then no point having here. It must be 
documented in the client binding. But then, what is this for in the 
first place?

> +
> +Some vaules of properties are defined in 'dt-bindings/gce/mt8173-gce.h'. Such as
> +thread number, sub-system ids, thread priority, event ids.
> +
> +Example:
> +
> +	gce: gce@...12000 {

mailbox@...

> +		compatible = "mediatek,mt8173-gce";
> +		reg = <0 0x10212000 0 0x1000>;
> +		interrupts = <GIC_SPI 135 IRQ_TYPE_LEVEL_LOW>;
> +		clocks = <&infracfg CLK_INFRA_GCE>;
> +		clock-names = "gce";
> +		thread-num = CMDQ_THR_MAX_COUNT;
> +		#mbox-cells = <4>;
> +	};
> +
> +Example for a client device:
> +
> +	mmsys: clock-controller@...00000 {
> +		compatible = "mediatek,mt8173-mmsys";
> +		mboxes = <&gce 0 2000 CMDQ_THR_PRIO_LOWEST 1>,
> +			 <&gce 1 2000 CMDQ_THR_PRIO_LOWEST 1>;
> +		gce-subsys = <SUBSYS_1400XXXX>;
> +		mutex-event-eof = <CMDQ_EVENT_MUTEX0_STREAM_EOF
> +				CMDQ_EVENT_MUTEX1_STREAM_EOF>;
> +
> +		...
> +	};