linux-kernel - Re: [PATCH v2 2/4] dt-bindings: mailbox: mediatek: gce-mailbox: Add reference to gce-props.yaml

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Date: Thu, 11 Jan 2024 17:31:10 +0000
From: Conor Dooley <conor@...nel.org>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	Singo Chang (張興國) <Singo.Chang@...iatek.com>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Johnson Wang (王聖鑫) <Johnson.Wang@...iatek.com>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Jason-ch Chen (陳建豪) <Jason-ch.Chen@...iatek.com>,
	Shawn Sung (宋孝謙) <Shawn.Sung@...iatek.com>,
	Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
	"conor+dt@...nel.org" <conor+dt@...nel.org>,
	Project_Global_Chrome_Upstream_Group <Project_Global_Chrome_Upstream_Group@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"krzysztof.kozlowski+dt@...aro.org" <krzysztof.kozlowski+dt@...aro.org>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	"jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
	"angelogioacchino.delregno@...labora.com" <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v2 2/4] dt-bindings: mailbox: mediatek: gce-mailbox: Add
 reference to gce-props.yaml

On Wed, Jan 10, 2024 at 04:36:20PM +0000, Jason-JH Lin (林睿祥) wrote:
> Hi Conor,
> 
> Thanks for the reviews.
> 
> On Wed, 2024-01-10 at 10:36 +0000, Conor Dooley wrote:
> > On Wed, Jan 10, 2024 at 02:35:30PM +0800, Jason-JH.Lin wrote:
> > > 1. Add "Provider" to the title to make it clearer.
> > > 2. Add reference to gce-props.yaml for adding mediatek,gce-events
> > > property.
> > 
> > I can see this from the diff. There's still no explanation here as to
> > why the mailbox provider needs to have a gce-event id. NAK until you
> > can
> > explain that.
> > 
> Sorry for missing the reason in commit message, I'll add it in the next
> version.
> 
> There are 2 reasons why the mailbox provider needs gce-events:
> 1. The mailbox provider here is CMDQ mailbox driver. It configures GCE
> hardware register by CPU directly. If we want to set the default value
> from 0 to 1 for specific gce-events during the initialization of CMDQ
> driver. We need to tell CMDQ driver what gce-events need to be set and
> I think such GCE hardware setting can get from its device node.

Why would someone want to set it to 1 or 0?
At what level will that vary? Per SoC? Per board? Something else?

> 2. We'll have the secure CMDQ mailbox driver in the future patch [1].
> It will request or reserve a mailbox channel, which is a dedicate GCE
> thread, as a secure IRQ handler. This GCE thread executes a looping
> instruction set that keeps waiting for the gce-event set from another
> GCE thread in the secure world. So we also need to tell the CMDQ driver
> what gce-event need to be waited.

Ditto here, what level does this vary at? Do different SoCs or different
boards/platforms dictate the value?
Could this channel be determined from the soc-specific compatible?

In other words, please explain in your commit message why this requires
a property and is not detectable from any existing mechanism. From
reading this I don't know what is preventing the secure mailbox channel
from picking a "random" unused channel.

Thanks,
Conor.

> [1] cmdq_sec_irq_notify_start() is where the GCE thread is requested to
> prepare a looping instruction set to wait for the gce-event.
> - 
> https://patchwork.kernel.org/project/linux-mediatek/patch/20231222045228.27826-9-jason-jh.lin@mediatek.com/
> 
> Regards,
> Jason-JH.Lin
> 
> > Cheers,
> > Conor.
> > 
> > > 
> > > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> > > ---
> > >  .../devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml   | 6
> > > ++++--
> > >  1 file changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git
> > > a/Documentation/devicetree/bindings/mailbox/mediatek,gce-
> > > mailbox.yaml
> > > b/Documentation/devicetree/bindings/mailbox/mediatek,gce-
> > > mailbox.yaml
> > > index cef9d7601398..728dc93117a6 100644
> > > --- a/Documentation/devicetree/bindings/mailbox/mediatek,gce-
> > > mailbox.yaml
> > > +++ b/Documentation/devicetree/bindings/mailbox/mediatek,gce-
> > > mailbox.yaml
> > > @@ -4,7 +4,7 @@
> > >  $id: 
> > > http://devicetree.org/schemas/mailbox/mediatek,gce-mailbox.yaml#
> > >  $schema: http://devicetree.org/meta-schemas/core.yaml#
> > >  
> > > -title: Mediatek Global Command Engine Mailbox
> > > +title: MediaTek Global Command Engine Mailbox Provider
> > >  
> > >  maintainers:
> > >    - Houlong Wei <houlong.wei@...iatek.com>
> > > @@ -57,6 +57,8 @@ required:
> > >    - clocks
> > >  
> > >  allOf:
> > > +  - $ref: mediatek,gce-props.yaml
> > > +
> > >    - if:
> > >        not:
> > >          properties:
> > > @@ -67,7 +69,7 @@ allOf:
> > >        required:
> > >          - clock-names
> > >  
> > > -additionalProperties: false
> > > +unevaluatedProperties: false
> > >  
> > >  examples:
> > >    - |
> > > -- 
> > > 2.18.0
> > > 

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