Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Received-SPF: Pass (protection.outlook.com: domain of xilinx.com designates
 149.199.62.198 as permitted sender) receiver=protection.outlook.com;
 client-ip=149.199.62.198; helo=xsj-pvapexch02.xlnx.xilinx.com;
Envelope-to: zajec5@gmail.com,
 seanga2@gmail.com,
 robh+dt@kernel.org,
 trini@konsulko.com,
 sjg@chromium.org,
 srinivas.kandagatla@linaro.org,
 krzysztof.kozlowski@canonical.com,
 ricardo@foundries.io,
 jorge@foundries.io,
 devicetree@vger.kernel.org,
 u-boot@lists.denx.de,
 linux-kernel@vger.kernel.org,
 rafal@milecki.pl
Message-ID: <16e788ec-28e4-11be-d1f8-5c5249a87c2d@xilinx.com>
Date:   Wed, 16 Feb 2022 15:28:06 +0100
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.6.0
Subject: Re: [PATCH] dt-bindings: nvmem: add U-Boot environment variables
 binding
Content-Language: en-US
To:     =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <zajec5@gmail.com>,
        Sean Anderson <seanga2@gmail.com>,
        Michal Simek <michal.simek@xilinx.com>,
        Rob Herring <robh+dt@kernel.org>,
        Tom Rini <trini@konsulko.com>, Simon Glass <sjg@chromium.org>
CC:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
        Ricardo Salveti <ricardo@foundries.io>,
        Jorge Ramirez-Ortiz <jorge@foundries.io>,
        <devicetree@vger.kernel.org>, <u-boot@lists.denx.de>,
        <linux-kernel@vger.kernel.org>,
        =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= <rafal@milecki.pl>
References: <20220215134925.32691-1-zajec5@gmail.com>
 <193f9354-5e1d-def8-c8ab-fbe88d8d9b8f@xilinx.com>
 <6679b98e-f5f0-8608-a36c-c0c41fb5ea6f@gmail.com>
 <3c690660-7e23-e11b-17b8-496882f3a34e@gmail.com>
From:   Michal Simek <michal.simek@xilinx.com>
In-Reply-To: <3c690660-7e23-e11b-17b8-496882f3a34e@gmail.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 8bit
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 16 Feb 2022 14:28:11.5802
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 166b31e7-f2c1-4257-667b-08d9f1588f82
X-MS-Exchange-CrossTenant-Id: 657af505-d5df-48d0-8300-c31994686c5c
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=657af505-d5df-48d0-8300-c31994686c5c;Ip=[149.199.62.198];Helo=[xsj-pvapexch02.xlnx.xilinx.com]
X-MS-Exchange-CrossTenant-AuthSource: DM3NAM02FT007.eop-nam02.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL3PR02MB8148
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,
        SPF_HELO_PASS,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham
        autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org


On 2/16/22 13:59, Rafał Miłecki wrote:
> On 15.02.2022 15:57, Sean Anderson wrote:
>> On 2/15/22 9:02 AM, Michal Simek wrote:
>>>
>>>
>>> On 2/15/22 14:49, Rafał Miłecki wrote:
>>>> From: Rafał Miłecki <rafal@milecki.pl>
>>>>
>>>> U-Boot uses environment variables for storing device setup data on
>>>> flash. That data usually needs to be accessed by a bootloader, kernel
>>>> and often user-space.
>>>>
>>>> This binding allows describing environment data location and its format
>>>> clearly. In some/many cases it should be cleaner than hardcoding &
>>>> duplicating that info in multiple places. Bootloader & kernel can share
>>>> DTS and user-space can try reading it too or just have correct data
>>>> exposed by a kernel.
>>>>
>>>> Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
>>>> ---
>>>>   .../devicetree/bindings/nvmem/u-boot,env.yaml | 58 +++++++++++++++++++
>>>>   MAINTAINERS                                   |  5 ++
>>>>   2 files changed, 63 insertions(+)
>>>>   create mode 100644 Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml 
>>>> b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
>>>> new file mode 100644
>>>> index 000000000000..a2b3a9b88eb8
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/nvmem/u-boot,env.yaml
>>>> @@ -0,0 +1,58 @@
>>>> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/nvmem/u-boot,env.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: U-Boot environment variables
>>>> +
>>>> +description: |
>>>> +  U-Boot uses environment variables to store device parameters and
>>>> +  configuration. They may be used for booting process, setup or keeping end 
>>>> user
>>>> +  info.
>>>> +
>>>> +  Data is stored on flash in a U-Boot specific format (header and NUL 
>>>> separated
>>>> +  key-value pairs).
>>>> +
>>>> +  This binding allows specifying data location and used format.
>>>> +
>>>> +maintainers:
>>>> +  - Rafał Miłecki <rafal@milecki.pl>
>>>> +
>>>> +allOf:
>>>> +  - $ref: nvmem.yaml#
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    oneOf:
>>>> +      - description: A standalone env data block
>>>> +        const: u-boot,env
>>>> +      - description: Two redundant blocks with active one flagged
>>>> +        const: u-boot,env-redundant-bool
>>>> +      - description: Two redundant blocks with active having higher counter
>>>> +        const: u-boot,env-redundant-count
>>>
>>> I am not convinced that this is the best way how to do it. Because in u-boot 
>>> implementation you would have to enable MTD partitions to get there.
>>> And the whole parsing will take a lot of time.
>>>
>>> I think the way how I think this can be handled is.
>>>
>>> # I don't think that discussion with Simon was finished.
>>> But for example (chosen or firmware node)
>>> chosen {
>>>      u-boot {
>>>          u-boot,env = <&qspi &part0>;
>>>          u-boot,env-redundant = <&qspi &part1>;
>>>          #or
>>>          u-boot,env = <&qspi 0 40000>;
>>>          u-boot,env-redundant = <&qspi 40000 40000>;
>>
>> What about when the environment is on top of UBI?
> 
> We can always add support for binding UBI volumes in DT. Somethig
> more-or-less like:
> 
> partitions {
>      compatible = "fixed-partitions";
>      #address-cells = <1>;
>      #size-cells = <1>;
> 
>      partition@0 {
>          compatible = "ubi";
>          label = "ubi";
>          reg = <0x0 0x1000000>;
> 
>          env0: partition-0 {
>              volume-name = "env";
>          };
> 
>          env1: partition-1 {
>              volume-id = <10>;
>          };
>      };
> };

If this is something ack by Rob I have no problem with it. But it has to go to 
schema.

M