RE: [EXT] Re: [PATCH v5 01/11] dt-bindings: arm: fsl: add imx-se-fw binding doc

Please find comments inline.


Regards
Varun

-----Original Message-----
From: Pankaj Gupta <pankaj.gupta@nxp.com>
Sent: Friday, August 25, 2023 12:56 PM
To: Varun Sethi <redacted>
Subject: FW: [EXT] Re: [PATCH v5 01/11] dt-bindings: arm: fsl: add imx-se-fw
binding doc



-----Original Message-----
From: Krzysztof Kozlowski <krzk@kernel.org>
Sent: Friday, August 25, 2023 12:16 AM
To: Rob Herring <robh@kernel.org>; Pankaj Gupta <pankaj.gupta@nxp.com>
Cc: shawnguo@kernel.org; s.hauer@pengutronix.de;
kernel@pengutronix.de; clin@suse.com; conor+dt@kernel.org;
pierre.gondois@arm.com; Jacky Bai [off-list ref]; Clark Wang
[off-list ref]; Wei Fang [off-list ref]; Peng Fan
[off-list ref]; Bough Chen [off-list ref];
festevam@gmail.com; dl-linux-imx [off-list ref];
davem@davemloft.net; krzysztof.kozlowski+dt@linaro.org; linux-arm-
kernel@lists.infradead.org; devicetree@vger.kernel.org; linux-
kernel@vger.kernel.org; Gaurav Jain [off-list ref];
alexander.stein@ew.tq-group.com; Sahil Malhotra
[off-list ref]; Aisheng Dong [off-list ref]; Varun
Sethi [off-list ref]; Greg Kroah-Hartman
[off-list ref]
Subject: [EXT] Re: [PATCH v5 01/11] dt-bindings: arm: fsl: add imx-se-fw
binding doc

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On 23/08/2023 14:43, Rob Herring wrote:

quoted

quoted

+                                                          |
+  +------------------------------------------------------ |
+                     |             |           |          |
+  userspace     /dev/ele_muXch0    |           |          |
+                           /dev/ele_muXch1     |          |
+                                         /dev/ele_muXchY  |
+                                                          |
+
+  When a user sends a command to the firmware, it registers its
+ device_ctx  as waiter of a response from firmware.
+
+  A user can be registered as receiver of command from the ELE.
+  Create char devices in /dev as channels of the form
+ /dev/ele_muXchY with X  the id of the driver and Y for each users.
+ It allows to send and receive  messages to the NXP EdgeLock Enclave
+ IP firmware on NXP SoC, where current  possible value, i.e., supported

SoC(s) are imx8ulp, imx93.

quoted

Looks like a bunch of Linux details which don't belong in the binding.

Why do you need your own custom interface to userspace? No one else
has a similar feature in their platforms? Something like virtio or
rpmsg doesn't work?

+Cc Greg,

I doubt they care. This is some stub-driver to pass messages from user-space
to the firmware. The interface is undocumented, without examples and no
user-space user.

Best regards,
Krzysztof

[Varun] The goal of the driver is to pass messages between firmware and user 
space/kernel consumers.
At the same time driver also enables firmware to use the storage via Linux 
user space. We do have
middleware applications that utilize the driver. These applications leverage 
cryptographic operations and trust
provisioning capabilities offered by the firmware. We can provide references 
to the middleware applications in the next
version of the patch. We do plan to enable the kernel crypto API interface to 
leverage operations provided by the firmware.

The operations that are exposed by the firmware are performance-sensitive and 
session-based (thus serialized). So, the Virtio/rpmsg model
is not suited for our implementation. Also, the secure enclave IP, with which 
the driver facilitates the communication is an opaque block
that doesn't fit the rpmsg model.