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Subject: Re: [PATCH v11 5/7] dt-bindings: display: Add Loongson display
 controller
Content-Language: en-US
To:     Rob Herring <robh@kernel.org>
Cc:     Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Roland Scheidegger <sroland@vmware.com>,
        Zack Rusin <zackr@vmware.com>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        "David S . Miller" <davem@davemloft.net>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Ilia Mirkin <imirkin@alum.mit.edu>,
        Qing Zhang <zhangqing@loongson.cn>,
        suijingfeng <suijingfeng@loongson.cn>,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org
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From:   Sui Jingfeng <15330273260@189.cn>
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On 2022/3/23 21:03, Rob Herring wrote:
> On Wed, Mar 23, 2022 at 11:38:55AM +0800, Sui Jingfeng wrote:
>> On 2022/3/23 04:55, Rob Herring wrote:
>>> On Tue, Mar 22, 2022 at 10:33:45AM +0800, Sui Jingfeng wrote:
>>>> On 2022/3/22 07:20, Rob Herring wrote:
>>>>> On Tue, Mar 22, 2022 at 12:29:14AM +0800, Sui Jingfeng wrote:
>>>>>> From: suijingfeng <suijingfeng@loongson.cn>
>>>>>>
>>>>> Needs a commit message.
>>>>>
>>>>>> Signed-off-by: suijingfeng <suijingfeng@loongson.cn>
>>>>>> Signed-off-by: Sui Jingfeng <15330273260@189.cn>
>>>>> Same person? Don't need both emails.
>>>> Yes,  suijingfeng@loongson.cn is my company's email. But it can not be used
>>>> to send patches to dri-devel,
>>>>
>>>> when send patches with this email, the patch will not be shown on patch
>>>> works.
>>>>
>>>> Emails  are either blocked or got  rejected  by loongson's mail server.  It
>>>> can only receive emails
>>>>
>>>> from you and other people, but not dri-devel. so have to use my personal
>>>> email(15330273260@189.cn) to send patches.
>>>>
>>>>>> ---
>>>>>>     .../loongson/loongson,display-controller.yaml | 230 ++++++++++++++++++
>>>>>>     1 file changed, 230 insertions(+)
>>>>>>     create mode 100644 Documentation/devicetree/bindings/display/loongson/loongson,display-controller.yaml
>>>>>>
>>>>>> diff --git a/Documentation/devicetree/bindings/display/loongson/loongson,display-controller.yaml b/Documentation/devicetree/bindings/display/loongson/loongson,display-controller.yaml
>>>>>> new file mode 100644
>>>>>> index 000000000000..7be63346289e
>>>>>> --- /dev/null
>>>>>> +++ b/Documentation/devicetree/bindings/display/loongson/loongson,display-controller.yaml
>>>>>> @@ -0,0 +1,230 @@
>>>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>>>> +%YAML 1.2
>>>>>> +---
>>>>>> +$id: http://devicetree.org/schemas/display/loongson/loongson,display-controller.yaml#
>>>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>>>> +
>>>>>> +title: Loongson LS7A1000/LS2K1000/LS2K0500 Display Controller Device Tree Bindings
>>>>>> +
>>>>>> +maintainers:
>>>>>> +  - Sui Jingfeng <suijingfeng@loongson.cn>
>>>>>> +
>>>>>> +description: |+
>>>>>> +
>>>>>> +  Loongson display controllers are simple which require scanout buffers
>>>>>> +  to be physically contiguous. LS2K1000/LS2K0500 is a SOC, only system
>>>>>> +  memory is available. LS7A1000/LS7A2000 is bridge chip which is equipped
>>>>>> +  with a dedicated video RAM which is 64MB or more, precise size can be
>>>>>> +  read from the PCI BAR 2 of the GPU device(0x0014:0x7A15) in the bridge
>>>>>> +  chip.
>>>>>> +
>>>>>> +  LSDC has two display pipes, each way has a DVO interface which provide
>>>>>> +  RGB888 signals, vertical & horizontal synchronisations, data enable and
>>>>>> +  the pixel clock. LSDC has two CRTC, each CRTC is able to scanout from
>>>>>> +  1920x1080 resolution at 60Hz. Each CRTC has two FB address registers.
>>>>>> +
>>>>>> +  For LS7A1000, there are 4 dedicated GPIOs whose control register is
>>>>>> +  located at the DC register space. They are used to emulate two way i2c,
>>>>>> +  One for DVO0, another for DVO1.
>>>>>> +
>>>>>> +  LS2K1000 and LS2K0500 SoC grab i2c adapter from other module, either
>>>>>> +  general purpose GPIO emulated i2c or hardware i2c in the SoC.
>>>>>> +
>>>>>> +  LSDC's display pipeline have several components as below description,
>>>>>> +
>>>>>> +  The display controller in LS7A1000:
>>>>>> +     ___________________                                     _________
>>>>>> +    |            -------|                                   |         |
>>>>>> +    |  CRTC0 --> | DVO0 ----> Encoder0 ---> Connector0 ---> | Monitor |
>>>>>> +    |  _   _     -------|        ^             ^            |_________|
>>>>>> +    | | | | |    -------|        |             |
>>>>>> +    | |_| |_|    | i2c0 <--------+-------------+
>>>>>> +    |            -------|
>>>>>> +    |   DC IN LS7A1000  |
>>>>>> +    |  _   _     -------|
>>>>>> +    | | | | |    | i2c1 <--------+-------------+
>>>>>> +    | |_| |_|    -------|        |             |             _________
>>>>>> +    |            -------|        |             |            |         |
>>>>>> +    |  CRTC1 --> | DVO1 ----> Encoder1 ---> Connector1 ---> |  Panel  |
>>>>>> +    |            -------|                                   |_________|
>>>>>> +    |___________________|
>>>>>> +
>>>>>> +  Simple usage of LS7A1000 with LS3A4000 CPU:
>>>>>> +
>>>>>> +    +------+            +-----------------------------------+
>>>>>> +    | DDR4 |            |  +-------------------+            |
>>>>>> +    +------+            |  | PCIe Root complex |   LS7A1000 |
>>>>>> +       || MC0           |  +--++---------++----+            |
>>>>>> +  +----------+  HT 3.0  |     ||         ||                 |
>>>>>> +  | LS3A4000 |<-------->| +---++---+  +--++--+    +---------+   +------+
>>>>>> +  |   CPU    |<-------->| | GC1000 |  | LSDC |<-->| DDR3 MC |<->| VRAM |
>>>>>> +  +----------+          | +--------+  +-+--+-+    +---------+   +------+
>>>>>> +       || MC1           +---------------|--|----------------+
>>>>>> +    +------+                            |  |
>>>>>> +    | DDR4 |          +-------+   DVO0  |  |  DVO1   +------+
>>>>>> +    +------+   VGA <--|ADV7125|<--------+  +-------->|TFP410|--> DVI/HDMI
>>>>>> +                      +-------+                      +------+
>>>>>> +
>>>>>> +  The display controller in LS2K1000/LS2K0500:
>>>>>> +     ___________________                                     _________
>>>>>> +    |            -------|                                   |         |
>>>>>> +    |  CRTC0 --> | DVO0 ----> Encoder0 ---> Connector0 ---> | Monitor |
>>>>>> +    |  _   _     -------|        ^              ^           |_________|
>>>>>> +    | | | | |           |        |              |
>>>>>> +    | |_| |_|           |     +------+          |
>>>>>> +    |                   <---->| i2c0 |<---------+
>>>>>> +    |   DC IN LS2K1000  |     +------+
>>>>>> +    |  _   _            |     +------+
>>>>>> +    | | | | |           <---->| i2c1 |----------+
>>>>>> +    | |_| |_|           |     +------+          |            _________
>>>>>> +    |            -------|        |              |           |         |
>>>>>> +    |  CRTC1 --> | DVO1 ----> Encoder1 ---> Connector1 ---> |  Panel  |
>>>>>> +    |            -------|                                   |_________|
>>>>>> +    |___________________|
>>>>>> +
>>>>>> +properties:
>>>>>> +  $nodename:
>>>>>> +    pattern: "^display-controller@[0-9a-f],[0-9a-f]$"
>>>>>> +
>>>>>> +  compatible:
>>>>>> +    oneOf:
>>>>>> +      - items:
>>>>>> +          - enum:
>>>>>> +              - loongson,ls7a1000-dc
>>>>>> +              - loongson,ls2k1000-dc
>>>>>> +              - loongson,ls2k0500-dc
>>>>>> +
>>>>>> +  reg:
>>>>>> +    maxItems: 1
>>>>>> +
>>>>>> +  interrupts:
>>>>>> +    maxItems: 1
>>>>>> +
>>>>>> +  '#address-cells':
>>>>>> +    const: 1
>>>>>> +
>>>>>> +  '#size-cells':
>>>>>> +    const: 0
>>>>>> +
>>>>>> +  i2c-gpio@0:
>>>>>> +    description: |
>>>>>> +      Built-in GPIO emulate i2c exported for external display bridge
>>>>> If you have i2c-gpio, that belongs at the DT top-level, not here.
>>>>>
>>>>>> +      configuration, onitor detection and edid read back etc, for ls7a1000
>>>>>> +      only. Its compatible must be lsdc,i2c-gpio-0. The reg property can be
>>>>> No, there's a defined i2c-gpio compatible already.
>>>> This is different from the i2c-gpio already defined under drivers/i2c/busses/i2c-gpio.c,
>>>> By design, my i2c-gpio is vendor specific properties, lsdc device driver create the i2c
>>>> adapter at runtime. These are 4 dedicated GPIOs whose control register is located at the
>>>> LSDC register space, not general purpose GPIOs with separate control register resource.
>>>> So i think it is the child node of display-controller@6,1, it belongs to LSDC.
>>>> It seems that put it at the DT top-level break the hierarchy and relationship.
>>> Okay, I see. Then just 'i2c' for the node names. You need a reference to
>>> i2c-controller.yaml for these nodes too.
>>>
>>> The compatible should not have an index in it.
>> OK, i will fix this at the next version. thanks.
>>>>>> +      used to specify a I2c adapter bus number, if you don't specify one
>>>>>> +      i2c driver core will dynamically assign a bus number. Please specify
>>>>> Bus numbers are a linux detail not relevant to DT binding.
>>>>>
>>>>>> +      it only when its bus number matters. Bus number greater than 6 is safe
>>>>>> +      because ls7a1000 bridge have 6 hardware I2C controller integrated.
>>>>>> +
>>>>>> +  i2c-gpio@1:
>>>>>> +    description: |
>>>>>> +      Built-in GPIO emulate i2c exported for external display bridge
>>>>>> +      configuration, onitor detection and edid read back etc, for ls7a1000
>>>>>> +      only. Its compatible must be lsdc,i2c-gpio-1.
>>>>>> +
>>>>>> +  ports:
>>>>>> +    $ref: /schemas/graph.yaml#/properties/ports
>>>>>> +
>>>>>> +    properties:
>>>>>> +      port@0:
>>>>>> +        $ref: /schemas/graph.yaml#/properties/port
>>>>>> +        description: output port node connected with DPI panels or external encoders, with only one endpoint.
>>>>>> +
>>>>>> +      port@1:
>>>>>> +        $ref: /schemas/graph.yaml#/properties/port
>>>>>> +        description: output port node connected with DPI panels or external encoders, with only one endpoint.
>>>>>> +
>>>>>> +    required:
>>>>>> +      - port@0
>>>>>> +      - port@1
>>>>>> +
>>>>>> +required:
>>>>>> +  - compatible
>>>>>> +  - reg
>>>>>> +  - interrupts
>>>>>> +  - ports
>>>>>> +
>>>>>> +additionalProperties: false
>>>>>> +
>>>>>> +examples:
>>>>>> +  - |
>>>>>> +    #include <dt-bindings/interrupt-controller/irq.h>
>>>>>> +    bus {
>>>>>> +
>>>>>> +        #address-cells = <3>;
>>>>>> +        #size-cells = <2>;
>>>>>> +        #interrupt-cells = <2>;
>>>>>> +
>>>>>> +        display-controller@6,1 {
>>>>>> +            compatible = "loongson,ls7a1000-dc";
>>>>>> +            reg = <0x3100 0x0 0x0 0x0 0x0>;
>>>>>> +            interrupts = <28 IRQ_TYPE_LEVEL_HIGH>;
>>>>>> +
>>>>>> +            #address-cells = <1>;
>>>>>> +            #size-cells = <0>;
>>>>>> +
>>>>>> +            i2c-gpio@0 {
>>>>>> +                compatible = "lsdc,i2c-gpio-0";
>>>>>> +                reg = <6>;
>>> 'reg' needs to be documented with some description of what 6 and 7
>>> represent. If they are the control register offset, then make the
>>> address translatable (use 'ranges' and define the size).
>> By design, the reg property is used to specify a I2c adapter bus number,
>> if we don't specify one, i2c driver core will dynamically assign a bus number.
>> then the nr of the i2c adapter will started from 0. I want is start from 6
>> to avoid potential conflict feature hardware I2C driver.
>>
>> Because LS7A1000 bridge chip have 6 hardware I2C controller integrated,
>> but its driver is not up-streamed yet. By default these hardware I2C controller's
>> nr is started from 0.
> Linux's numbering doesn't belong in DT. So no, you can't use 'reg' in
> that way.
Then,  can i use something like lsdc,nr = <6> ?
>> Even through i2c driver core can dynamically generate a number, i still want it
>> to be fixed and keep consistent and explicit. That is, i2c6 is for display pipe 0,
>> i2c7 is for display pipe 1. This follow the convention and flexible enough.
> You may want that, but that is not how the kernel works. Specific
> numbers are not guaranteed. I'm sure you've seen this for disks, network
> interfaces, etc.
>
> Rob

2c_bit_add_numbered_bus() will guarantee it for you as long as If no 
devices have pre-been declared for this bus.

you can read the comment of 2c_bit_add_numbered_bus() at 
drivers/i2c/i2c-core-base.c