tdo_panel: bcm27xx-gpu: Add dsi panel driver;

[flash-fea]

- Add vc4-kms-dsi-panel-overlay.dts for tdo panel compatiable.
- Simplify add panel-tdo-dsi-v1.c as module to driver tdo panel.
- __overrides__ parameter can be add in config.txt for customers.

[flash-fea]

whether the addition was successful?

[pelwell]

The partitioning of the code looks good, and checkpatch is happy.

This isn't my field of expertise so there is limited input I can give regarding the driver itself - perhaps @6by9 has some comments - but there are a few things I have spotted:

1. The authorship of the code (and therefore the permission to publish it) is a bit vague. The comment at the top of the driver file says Copyright (C) 2024 Waveshare International Limited, but the footer says MODULE_AUTHOR("LK <support@tdo.com>"); and MODULE_DESCRIPTION("TDO DSI panel driver");, none of which seems to match your GitHub user account.
2. I see a number of dev_err() used for what look like debug output. I do the same myself, but it shouldn't still be around in a production driver. If the information is useful to users, demote it to INFO level or lower, otherwise go for dev_dbg or deletion.

[6by9]

Sorry I had all my review comments pending on the 6.12 version. Now posted.
I suspect that they all apply here too.

Largely the same as pelwell has commented with regard pr_err debugging and authorship, but also a couple of other points.
I suspect that you've copied the panel-waveshare-dsi-v2 driver and amended for your panels, but it'd nice to have that confirmed. That may not have been the best base as it isn't a driver that has been reviewed by upstream, but that isn't critical for a Pi specific product.

[flash-fea]

yes,some informations need to change,about two dev_err() only use in debug to find by text easyier,but forget to recover.

[pelwell]

This also needs updating

[pelwell]

Delete, as 6by9 says

[flash-fea]

delete all? reset-gpios maybe use in future,i see these were added also in other dts.

[6by9]

You can add it at a later stage via an override if it is needed.

As it stands the driver will claim a totally unrelated GPIO for no particular reason. GPIO 47 isn't necessarily unused or even present on all devices, so could actually cause issues if left in.

[flash-fea]

some my device's driver need it, as how i write to overlay in use

[6by9]

For those devices that do require it you can add an additional fragment to configure it which can be enabled by the relevant override.

A similar case is https://github.com/raspberrypi/linux/blob/rpi-6.12.y/arch/arm/boot/dts/overlays/edt-ft5406.dtsi#L11-L16 where we want to add the touchscreen-inverted-x; property on demand, triggered by the invx override

With the driver calling devm_gpiod_get_optional, the driver doesn't need it. It's permitted to call any of the gpiod_ functions with the returned (NULL) handle.

[flash-fea]

like this?
reset_pin = <&panel>,"reset-gpios:47";
and modify driver for devm_gpiod_get_optional.

[pelwell]

Close:

reset_pin = <&panel>,"reset-gpios:0=",<&gpio>, 
            <&panel>,"reset-gpios:4=47",
            <&panel>,"reset-gpios:8=1";

will create the reset-gpios property if you use the reset_pin parameter, but 6by9 was suggesting that you would build that into a product declaration:

new_panel_needing_reset = <&panel>, "compatible=tdo,new-panel-needing-reset",
            <&panel>,"reset-gpios:0=",<&gpio>,
            <&panel>,"reset-gpios:4=47",
            <&panel>,"reset-gpios:8=1";

But it might be cleaner to have a dormant fragment that gets enabled as needed.

[6by9]

The driver is already using

ctx->reset = devm_gpiod_get_optional(&dsi->dev, "reset", GPIOD_OUT_LOW);

That means that ctx->reset will not return an error if reset-gpios is missing.

Add an additional fragment along the lines of:

	fragment@10 {
		target = <&panel>;
		reset_gpio_frag: __dormant__ {
			reset-gpios = <&gpio 47 1>;
		};
	};
	__overrides__ {
		reset_pin = <0>, "+10", 
				<&reset_gpio_frag>, "reset-gpios:4";
	};

You can then have dtoverlay=vc4-kms-dsi-tdo-panel,reset_pin=47 to enable the reset gpio and set it to 47 (or whatever other GPIO number you wish to use).

Just looking through the various Pi variants, gpio 47 is used for:

• Pi1A/B: SD card detect
• Pi1A+, B+, 2B, 3B, Zero, ZeroW: Activity LED
• Pi 3B+/A+, CM3, CM4, 02W, CM0 : I2C to SMPS
• CM1: EMMC_ENABLE_N

This is why I say it can't be claimed generically by the overlay.
(Pi5 appears to use it for 2712_WAKE)

[flash-fea]

this reset pin is not decided yet,can you give me a suggest? now dts add this->
+fragment@4 {

•   target = <&panel>;
  

•   reset_gpio_frag: __dormant__ {
  

•   	reset-gpios = <&gpio 47 1>;
  

•   };
  

• };

dsi0 = <&dsi_frag>, "target:0=",<&dsi0>,
<&i2c_frag>, "target:0=",<&i2c_csi_dsi0>;

• reset_pin = <0>, "+10",

•          <&reset_gpio_frag>, "reset-gpios:4";
  

[flash-fea]

ctx->reset = devm_gpiod_get_optional(&dsi->dev, "reset", GPIOD_OUT_LOW);
if (IS_ERR(ctx->reset))
dev_warn(&dsi->dev, "Couldn't get the reset GPIO\n");

[pelwell]

No user needs to see this - dev_dbg or delete.

[pelwell]

It is preferred for successful probing to generate minimal output. Perhaps defer this line to after the number of lanes is available and combine the two?

[pelwell]

You really don't need this.

[flash-fea]

struct tdo_panel *ctx = mipi_dsi_get_drvdata(dsi);

gpiod_set_value_cansleep(ctx->reset, 0);

like this,is it ok?

[pelwell]

I was referring to the dev_info()

[6by9]

I've just noticed that someone is upstreaming the Waveshare DSI display drivers to mainline at present

V2 displays https://lore.kernel.org/dri-devel/20260413-waveshare-dsi-touch-v3-21-3aeb53022c32@oss.qualcomm.com/

https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/bridge/waveshare-dsi.c for the V1 displays is already merged.
https://lore.kernel.org/dri-devel/20260412-ws-lcd-v3-0-db22c2631828@oss.qualcomm.com/T/ is extending that.

At some point I'll update the overlays and delete the old panel-waveshare-dsi and panel-waveshare-dsi-v2 drivers.

There are a couple of tdo panel drivers already in mainline, so if any of them match these new panels then the configuration really should be added to those drivers rather than this new one.
https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/panel/panel-tdo-tl070wsh30.c
https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/panel/panel-tpo-td028ttec1.c
https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/panel/panel-tpo-td043mtea1.c

[flash-fea]

my company need only one driver to use all our mipi panel,it seems to add some after this request finish.

[pelwell]

This is not true - there is no default value, because you can't enable the reset pin without assigning a value.

[pelwell]

The number after the "+" is the number of the fragment to enable, which in this case should be 4.

[6by9]

my company need only one driver to use all our mipi panel,it seems to add some after this request finish.

You haven't actually answered my questions as to whether you are actually representing TDO as the panel manufacturer, and whether you are creating a product to use this with a Raspberry Pi.

You may prefer having a single driver for all displays, but the mainline Linux folks may disagree and wish the panels to be clustered into similar families or by controller IC.
We have little interest in merging drivers here that aren't for use with a Raspberry Pi.

[flash-fea]

Yes, I work at TDO. The company is currently expanding into the Raspberry Pi market, and in fact, some customers are already using it in a variety of scenarios. Merging into the branch will facilitate future work.

[pelwell]

I've split the long README line