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

[houlong wei <houlong.wei@mediatek.com>]

On Fri, 2018-07-06 at 04:08 +0800, Rob Herring wrote:
> On Tue, Jul 3, 2018 at 5:39 PM houlong wei <houlong.wei@mediatek.com> wrote:
> >
> > On Tue, 2018-07-03 at 10:30 +0800, Rob Herring wrote:
> > > 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@mediatek.com>
> > > > Signed-off-by: HS Liao <hs.liao@mediatek.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.
> > >
> >
> > 'thread-num' is used to configure the GCE thread number, which is the
> > channel number of gce mailbox. This property is read in
> > cmdq_probe()/mtk-cmdq-mailbox.c and a mailbox's channel array is
> > allocated according to the number.
> > Since the thread number may be different on different SoC, we wish it
> > could be configured in device tree.
> 
> You should have different compatible strings for different SoCs and
> can imply the number of threads from that.
> 

Thanks. Will remove 'thread-num' form device tree and put it in match
table of cmdq dirver.

> Or if the number of threads doesn't vary greatly, just allocate the
> max # of channels. Or allocate the per thread data when a thread is
> actually in use.
> 
> >
> > > > +- #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?
> >
> > You mean the new added property 'gce-subsys'?
> > It is used for GCE to distinguish the high 16-bit of a hardware register
> > address. When a client driver packets a register setting into a GCE
> > instruction, it uses a sub-system code and register offset instead of
> > the 32-bit register address.
> > Since sub-system code may be different on different SoC, we wish it
> > could be configured in device tree.
> 
> Okay. It needs a vendor prefix and to specify the size and type of the value.
> 

Will do.

> >
> > >
> > > > +
> > > > +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?
> >
> > Since display driver will use GCE firstly, so we will move the
> > description to
> > 'Documentation/devicetree/bindings/display/mediatek/mediatek,disp.txt'
> > when display driver start using the GCE driver.
> > Is that ok?
> 
> Not sure. I don't understand how it is used.
> 
> > > > +
> > > > +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@10212000 {
> > >
> > > mailbox@...
> >
> > Will do.
> >
> > >
> > > > +           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@14000000 {
> > > > +           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>;
> > > > +
> > > > +           ...
> > > > +   };
> >
> >
> > --
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