linux-kernel - Re: [PATCH 1/1] arm64: dts: imx8qxp-mek: add cm40

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Date: Fri, 5 Apr 2024 20:21:18 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Frank Li <Frank.li@....com>
Cc: Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>,
 "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
 <devicetree@...r.kernel.org>,
 "open list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" <imx@...ts.linux.dev>,
 "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
 <linux-arm-kernel@...ts.infradead.org>,
 open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] arm64: dts: imx8qxp-mek: add cm40_i2c, wm8960/wm8962
 and sai[0,1,4,5]

On 05/04/2024 16:46, Frank Li wrote:
> On Fri, Apr 05, 2024 at 08:41:59AM +0200, Krzysztof Kozlowski wrote:
>> On 04/04/2024 18:19, Frank Li wrote:
>>> imx8qxp-mek use two kind audio codec, wm8960 and wm8962. Using dummy gpio
>>> i2c bus mux to connect both i2c devices. One will probe failure and other
>>> will probe success when devices driver check whoami. So one dtb can cover
>>> both board configuration.
>>
>> I don't understand it. Either you add real device or not. If one board
>> has two devices, then why do you need to check for failures?
>>
>> Anyway, don't add fake stuff to DTS.
> 
> NAK can't resolve the problem. It should be common problem for long time
> cycle boards. Some chipes will be out life cycle. such as some sensor. So
> chips on boards have been replace by some pin to pin compatible sensor. For
> example: 
> 	old boards: use sensor A with address 0x1a
> 	new bench: use sensor B with address 0x1b.
> 
> You can treat it as two kind boards, RevA or RevB. But most user want to
> use one dtb to handle such small differences. For this case, it should be
> simple. Just add a super set.
> 	i2c
> 	{
> 		sensorA@1a
> 		{
> 		}
> 		sensorB@1b
> 		{
> 		}	
> 	}
> 
> It also depend on whoami check by i2c devices. Only A or B will probe.
> 
> wm8960 and wm8962 are more complex example.  wm8960 is out of life. But
> wm8962 and wm8960 have the same i2c address. The current i2c frame can't
> allow the same i2c address in one i2c bus.
> 
> You are feel to NAK my method, but I hope you also provide constructive
> solution to help resolve the problem.

Yes, we resolved it long time ago. Your bootloader can (usually easily)
detect revision of the board and load appropriate DTS or DTS+DTSO.

Best regards,
Krzysztof