linux-kernel - Re: [PATCH v3 8/9] mailbox: mediatek: Add CMDQ secure mailbox driver

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Message-ID: <ae7dba29db2591ca3d09020e1cebbbbbc24b1f18.camel@mediatek.com>
Date: Thu, 28 Dec 2023 02:02:03 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: "jassisinghbrar@...il.com" <jassisinghbrar@...il.com>,
	"matthias.bgg@...il.com" <matthias.bgg@...il.com>,
	Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>,
	"angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>, "robh+dt@...nel.org"
	<robh+dt@...nel.org>, "krzysztof.kozlowski+dt@...aro.org"
	<krzysztof.kozlowski+dt@...aro.org>, "chunkuang.hu@...nel.org"
	<chunkuang.hu@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	Singo Chang (張興國) <Singo.Chang@...iatek.com>,
	Johnson Wang (王聖鑫) <Johnson.Wang@...iatek.com>,
	"linux-media@...r.kernel.org" <linux-media@...r.kernel.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>, "mchehab@...nel.org" <mchehab@...nel.org>,
	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>
Subject: Re: [PATCH v3 8/9] mailbox: mediatek: Add CMDQ secure mailbox driver

On Wed, 2023-12-27 at 06:13 +0000, Jason-JH Lin (林睿祥) wrote:
> Hi CK,
> 
> Thanks for the reviews.
> 
> On Tue, 2023-12-26 at 06:46 +0000, CK Hu (胡俊光) wrote:
> > Hi, Jason:
> > 
> > On Fri, 2023-12-22 at 12:52 +0800, Jason-JH.Lin wrote:
> > > To support secure video path feature, GCE have to read/write
> > > registgers
> > > in the secure world. GCE will enable the secure access permission
> > > to
> > > the
> > > HW who wants to access the secure content buffer.
> > > 
> > > Add CMDQ secure mailbox driver to make CMDQ client user is able
> > > to
> > > sending their HW settings to the secure world. So that GCE can
> > > execute
> > > all instructions to configure HW in the secure world.
> > > 
> > > Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> > > ---
> > 
> > [snip]
> > 
> > > +
> > > +static int cmdq_sec_session_init(struct cmdq_sec_context
> > > *context)
> > > +{
> > > +	int err = 0;
> > > +
> > > +	if (context->state >= IWC_SES_OPENED) {
> > > +		pr_debug("session opened:%u", context->state);
> > > +		return 0;
> > > +	}
> > > +
> > > +	switch (context->state) {
> > > +	case IWC_INIT:
> > > +		err = cmdq_sec_init_context(&context->tee_ctx);
> > > +		if (err)
> > > +			return err;
> > > +		context->state = IWC_CONTEXT_INITED;
> > > +	fallthrough;
> > > +	case IWC_CONTEXT_INITED:
> > > +		if (context->iwc_msg) {
> > > +			pr_err("iwcMessage not NULL:%p", context-
> > > > iwc_msg);
> > > 
> > > +			return -EINVAL;
> > > +		}
> > > +
> > > +		err = cmdq_sec_allocate_wsm(&context->tee_ctx,
> > > &context->iwc_msg,
> > > +					    sizeof(struct
> > > iwc_cmdq_message_t));
> > > +		if (err)
> > > +			return err;
> > > +
> > > +		context->state = IWC_WSM_ALLOCATED;
> > > +	fallthrough;
> > 
> > Squash cmdq_sec_session_init() into cmdq_sec_mbox_of_xlate() and
> > drop
> > the context->state.
> > 
> > Regards,
> > CK
> > 
> 
> cmdq_sec_session_init() is called in the first
> cmdq_sec_task_submit().
> It means we don't need to connect a session to TEE or allocate share
> memory if no one submit secure task.
> 
> On the other hand, optee may load slower than cmdq secure driver. If
> we
> move it to xlate secure session may init fail.

For driver probe dependency, you could refer to [1]. I would like
resource allocation and free to be symmetric. So maybe allocate/free in
probe/remove or starup/shutdown. If the secure driver is probed, I
think it would finally allocate secure resource. So later allocation
has no much benefit and make code more complicated. 

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/gpu/drm/mediatek?h=next-20231222&id=c8048dd0b07df68724805254b9e994d99e9a7af4

Regards,
CK


> 
> Regards,
> Jason-JH.Lin