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Date: Sat, 26 Mar 2022 18:04:46 +0800
From: Sui Jingfeng <15330273260@....cn>
To: Rob Herring <robh@...nel.org>
Cc: Qing Zhang <zhangqing@...ngson.cn>,
David Airlie <airlied@...ux.ie>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
linux-kernel@...r.kernel.org, Sam Ravnborg <sam@...nborg.org>,
Krzysztof Kozlowski <krzk@...nel.org>,
Dan Carpenter <dan.carpenter@...cle.com>,
devicetree@...r.kernel.org, suijingfeng <suijingfeng@...ngson.cn>,
Thomas Zimmermann <tzimmermann@...e.de>,
Roland Scheidegger <sroland@...are.com>,
Andrey Zhizhikin <andrey.zhizhikin@...ca-geosystems.com>,
dri-devel@...ts.freedesktop.org,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
linux-mips@...r.kernel.org,
"David S . Miller" <davem@...emloft.net>
Subject: Re: [PATCH v11 5/7] dt-bindings: display: Add Loongson display
controller
On 2022/3/24 21:26, Rob Herring wrote:
> On Thu, Mar 24, 2022 at 09:48:19AM +0800, Sui Jingfeng wrote:
>> 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@...ngson.cn>
>>>>>>>>
>>>>>>> Needs a commit message.
>>>>>>>
>>>>>>>> Signed-off-by: suijingfeng <suijingfeng@...ngson.cn>
>>>>>>>> Signed-off-by: Sui Jingfeng <15330273260@....cn>
>>>>>>> Same person? Don't need both emails.
>>>>>> Yes, suijingfeng@...ngson.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@....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@...ngson.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
> I didn't say it wasn't possible. It is not best practice. Grep
> i2c_bit_add_numbered_bus and see how many users there are.
i2c-gpio.c at drivers/i2c/busses/ just do the same thing.
+ nvidia,bpmp-bus-id: + $ref: /schemas/types.yaml#/definitions/uint32 +
description: Indicates the I2C bus number this DT node represents, + as
defined by the BPMP firmware.
> Even if the kernel allows specifying bus numbers,your Linux bus numbers don't
> belong in DT.
Again, Does does devicetree specification prohibit this?
Nvidia also put i2c bus number in the DT, we learn that from nvidia. [1][2]
[1] Documentation/devicetree/bindings/i2c/nvidia,tegra186-bpmp-i2c.yaml
[2]
https://lore.kernel.org/all/20211208143306.534700-1-thierry.reding@gmail.com/
>
> Rob
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