RE: [PATCH 4/4] dt-bindings: serial: fsl-lpuart: add imx8ulp compatible string

[Sherry Sun]

> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> Sent: 2023年6月25日 18:18
> To: Sherry Sun <sherry.sun@xxxxxxx>; robh+dt@xxxxxxxxxx;
> krzysztof.kozlowski+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx;
> shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx;
> Shenwei Wang <shenwei.wang@xxxxxxx>; gregkh@xxxxxxxxxxxxxxxxxxx
> Cc: devicetree@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> Subject: Re: [PATCH 4/4] dt-bindings: serial: fsl-lpuart: add imx8ulp
> compatible string
> 
> On 25/06/2023 11:48, Sherry Sun wrote:
> > LPUART driver adds a new compatible string for imx8ulp, and imx93 is
> 
> What driver adds or not, is not really correct argument for compatibility.
> There are plenty of compatible devices which have both device ID entries in
> the driver. Why would you drop their compatibility between each other? It
> does not work like that... Provide clear rationale for this.

Hi Krzysztof, 
We take imx7ulp lpuart as the basic version IP, then imx8ulp adds some improved features based on the imx7ulp lpuart IP.
Actually imx8ulp can also work with the imx7ulp version, we can say it is compatible with imx7ulp, but we need to enable those new features by default on imx8ulp, so we added the imx8ulp-lpuart compatible in lpuart driver. So for this case, maybe compatible = "fsl,imx8ulp-lpuart", "fsl,imx7ulp-lpuart" is correct for imx8ulp platform, right?

Then we have the imx93 family with the same lpuart version as imx8ulp, so how should we handle the compatible string for imx93 platform? Maybe compatible = "fsl,imx93-lpuart", "fsl,imx8ulp-lpuart", "fsl,imx7ulp-lpuart"? But three compatible strings looks too long for me, so I want to drop imx7ulp-lpuart and take imx8ulp-lpuart as the basic compatible string for imx93 and later others imx9 series, I am not sure if it is suitable, some suggestions here will be appreciate, thanks!

Best Regards
Sherry

> 
> > much more compatible with imx8ulp than imx7ulp, so correct the
> > dt-binding here.
> >
> 
> "Much more compatible" is too vague.
> 
> 
> Best regards,
> Krzysztof