linux-kernel - RE: [PATCH 1/2] drm/panel: panel-simple: Add generic panel-dsi driver

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Message-ID:
 <PAWPR02MB9281557BDDA960812412E0D59B122@PAWPR02MB9281.eurprd02.prod.outlook.com>
Date: Mon, 22 Apr 2024 14:05:01 +0000
From: Johan Adolfsson <Johan.Adolfsson@...s.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, Neil Armstrong
	<neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, Sam
 Ravnborg <sam@...nborg.org>, Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>, Rob Herring <robh+dt@...nel.org>, Krzysztof
 Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Conor Dooley
	<conor+dt@...nel.org>, Thierry Reding <thierry.reding@...il.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, kernel
	<kernel@...s.com>, Johan Adolfsson <Johan.Adolfsson@...s.com>
Subject: RE: [PATCH 1/2] drm/panel: panel-simple: Add generic panel-dsi driver

Hi,
Sorry for delayed response, still investigating why these mails didn't reach my inbox as expected..

-----Original Message-----
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> 
Sent: den 19 april 2024 01:06
To: Johan Adolfsson <Johan.Adolfsson@...s.com>; Neil Armstrong <neil.armstrong@...aro.org>; Jessica Zhang <quic_jesszhan@...cinc.com>; Sam Ravnborg <sam@...nborg.org>; Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>; Maxime Ripard <mripard@...nel.org>; Thomas Zimmermann <tzimmermann@...e.de>; David Airlie <airlied@...il.com>; Daniel Vetter <daniel@...ll.ch>; Rob Herring <robh+dt@...nel.org>; Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>; Conor Dooley <conor+dt@...nel.org>; Thierry Reding <thierry.reding@...il.com>
Cc: dri-devel@...ts.freedesktop.org; linux-kernel@...r.kernel.org; devicetree@...r.kernel.org; kernel <kernel@...s.com>
Subject: Re: [PATCH 1/2] drm/panel: panel-simple: Add generic panel-dsi driver

On 18/04/2024 16:01, Johan Adolfsson wrote:
> Add generic panel-dsi panel, similar to panel-dpi that can have it's 
> timing, lanes and flags overridden by devicetree.
> Add some dev_err() and dev_warn() calls.
> 

...

>>  		/* sentinel */
>>  	}
>> @@ -4992,17 +5051,28 @@ static int panel_simple_dsi_probe(struct mipi_dsi_device *dsi)
>>  		return -ENODEV;
>>  
>>  	err = panel_simple_probe(&dsi->dev, &desc->desc);
>> +	if (err)
>> +		dev_err(&dsi->dev, "%s: err %i\n", __func__, err);

>This looks like debugging code.
I added it since you don't really get any good hints on where things fails if they do it.
Debugging code or not depends on the definition I guess - it helps the user track down a faulty devicetree,
or as in the case below mismatch with the DSI driver.

...
>>  	dsi->format = desc->format;
>>  	dsi->lanes = desc->lanes;
>> +	of_property_read_u32(dsi->dev.of_node, "lanes", &dsi->lanes);
>
>Is this defined in the binding?

Apparently not which I assumed. Other bindings mentions dsi-lanes, but I guess "num-dsi-lanes" would be more correct.

>>  	err = mipi_dsi_attach(dsi);
>>  	if (err) {
>>  		struct panel_simple *panel = mipi_dsi_get_drvdata(dsi);
>>  
>> +		dev_err(&dsi->dev, "probe attach err: %i", err);
>
>Do not introduce unrelated code changes.

As before, it helps the user who has a messed up devicetree find out, since we now gets some more configurability using devicetree.
Would it be acceptable as a separate commit, or should I simply skip this?


>Best regards,
>Krzysztof

Thanks!

Best regards
/Johan