From: Krzysztof Kozlowski <krzk@kernel.org>
To: Oleksii Moisieiev <Oleksii_Moisieiev@epam.com>
Cc: "robh+dt@kernel.org" <robh+dt@kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Cristian Marussi <cristian.marussi@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 0/1] dt-bindings: arm: Add scmi_devid paramter for
Date: Tue, 22 Feb 2022 09:06:25 +0100 [thread overview]
Message-ID: <7f17ab8f-429f-d2e0-8f5f-bfa2dd19cc49@kernel.org> (raw)
In-Reply-To: <20220221213932.GA164964@EPUAKYIW015D>
On 21/02/2022 22:39, Oleksii Moisieiev wrote:
> Hi Krzysztof,
>
> On Mon, Feb 21, 2022 at 10:01:43PM +0100, Krzysztof Kozlowski wrote:
>> On 21/02/2022 18:26, Oleksii Moisieiev wrote:
>>> Introducing new parameter called scmi_devid to the device-tree bindings.
>>> This parameter should be set for the device nodes, which has
>>> clocks/power-domains/resets working through SCMI.
>>> Given parameter should set the device_id, needed to set device
>>> permissions in the Firmware. This feature will be extremely useful for
>>> the virtualized systems, which has more that one Guests running on the
>>> system at the same time or for the syestems, which require several
>>> agents with different permissions. Trusted agent will use scmi_devid to
>>> set the Device permissions for the Firmware (See Section 4.2.2.10 [0]
>>> for details).
>>> Agents concept is described in Section 4.2.1 [0].
>>>
>>> scmi_devid in Device-tree node example:
>>> usb@e6590000
>>> {
>>> scmi_devid = <19>;
>>> clocks = <&scmi_clock 3>, <&scmi_clock 2>;
>>> resets = <&scmi_reset 10>, <&scmi_reset 9>;
>>> power-domains = <&scmi_power 0>;
>>> };
>>
>> And how do you prevent DT overlay adding such devid to any other node
>> thus allowing any other device to send requests with given devid?
>>
> Thank you for the quick response.
> scmi_devid value will be used only by Trusted Agent when the device
> permissions are set. Non-trusted agents, which in our case are
> represented as Guest OS are using scmi drivers, already present in linux
> kernel, ignores scmi_devid and uses scmi_clocks, scmi_power, scmi_reset
> nodes to access to SCMI protocol.
Ah, ok.
>
>> Plus few technicalities:
>> 1. Hyphen, not underscore in property name, so scmi-devid.
>
> Thanks for the tip, I will change that in v2.
Few more thoughts:
1. This looks specific to ARM SCMI, so you also need vendor prefix, so
something like:
arm,scmi-devid
arm,scmi-device-id
2. Does your example work properly? Passes dt_binding_check? Reg looks
different than unit-address.
>
>> 2. Your schema does is not selected by anything. How is it intended to
>> be used? Nothing is including it, either...
>>
>
> The idea is to use this parameter to set the device_id for the device in
> the device-tree, which matches to the device mapping in the Firmware, so
> Trusted Agent can use it to the device permissions.
> Please see Sections 4.2.2.10 and 4.2.1 [0] (Link was provided in the
> cover letter).
>
> I'm currently propose the new feature, called SCI mediator to Xen-devel
> community. Please see link [1] from cover letter for the details.
> In this feature - Xen is the Trusted Agent, which uses scmi_devid
> parameter to set the device permissions.
> We think that this parameter will be useful for other possible SCMI
> implementations, such as other hypervisor or SCMI backend server etc.
We talk about different things, I think. I was asking how is this schema
selected?
I gave it a fast try (dtbs_check) and it confirmed - schema does not
have an effect. It's a noop. You need something like "select: true", see:
Documentation/devicetree/bindings/nvmem/nvmem-consumer.yaml
or this schema should be included by other schemas... but then I would
be happy to see actual usage in this patchset (more commits...).
Best regards,
Krzysztof
next prev parent reply other threads:[~2022-02-22 8:06 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-21 17:26 [RFC PATCH 0/1] dt-bindings: arm: Add scmi_devid paramter for Oleksii Moisieiev
2022-02-21 17:26 ` [RFC PATCH 1/1] dt-bindings: arm: Add scmi_devid property description for SCMI Oleksii Moisieiev
2022-02-22 14:22 ` Rob Herring
2022-02-22 14:51 ` Oleksii Moisieiev
2022-02-22 18:25 ` Rob Herring
2022-02-21 21:01 ` [RFC PATCH 0/1] dt-bindings: arm: Add scmi_devid paramter for Krzysztof Kozlowski
2022-02-21 21:39 ` Oleksii Moisieiev
2022-02-22 8:06 ` Krzysztof Kozlowski [this message]
2022-02-22 8:55 ` Oleksii Moisieiev
2022-02-22 9:27 ` Krzysztof Kozlowski
2022-02-22 10:30 ` Oleksii Moisieiev
2022-02-22 11:16 ` Krzysztof Kozlowski
2022-02-22 13:54 ` Oleksii Moisieiev
2022-02-22 16:14 ` Sudeep Holla
2022-02-22 17:34 ` Oleksii Moisieiev
2022-02-24 2:51 ` Stefano Stabellini
2022-02-24 9:32 ` Cristian Marussi
2022-02-24 22:22 ` Stefano Stabellini
2022-03-01 14:55 ` Oleksii Moisieiev
2022-03-04 11:21 ` Sudeep Holla
2022-03-04 11:18 ` Sudeep Holla
2022-02-22 11:00 ` Cristian Marussi
2022-02-22 13:51 ` Oleksii Moisieiev
2022-02-22 16:06 ` Sudeep Holla
2022-02-22 17:15 ` Oleksii Moisieiev
2022-02-24 11:54 ` Sudeep Holla
2022-02-24 22:51 ` Stefano Stabellini
2022-02-24 23:34 ` Stefano Stabellini
2022-03-04 11:12 ` Sudeep Holla
2022-03-05 0:45 ` Stefano Stabellini
2022-04-29 21:46 ` Rob Herring
2022-03-01 16:10 ` Oleksii Moisieiev
2022-03-01 16:05 ` Oleksii Moisieiev
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