On Tue, Feb 14, 2023 at 10:33 AM Krzysztof Kozlowski
[off-list ref] wrote:

On 14/02/2023 09:54, Sergio Paracuellos wrote:

quoted

quoted

quoted

      return 0;

@@ -143,6 +147,10 @@ static int mt7621_wdt_probe(struct platform_device *pdev)
      if (!drvdata)
              return -ENOMEM;

+     drvdata->sysc = syscon_regmap_lookup_by_compatible("mediatek,mt7621-sysc");
+     if (IS_ERR(drvdata->sysc))
+             return PTR_ERR(drvdata->sysc);

This should be the backup/error path for original code using syscon
property. Looking up by compatible is really not portable/re-usable.

I can change the code in the way you are pointing out here but...
Why is it not re-usable? Compatible is not supposed to be changed
since in other cases the DTB ABI will be broken. I am totally lost
about what is an ABI breakage, then.

How do you use it on other platform?

I see, thanks.

So if I am understanding you correctly I have to maintain the
'mediatek,sysctl' phandle and use it in the first instance and if it
fails I have to use regmap_loopup_by_compatible() stuff, right?
Something like:

...

drvdata->sysc = syscon_regmap_lookup_by_phandle(np, "mediatek,sysctl");
if (IS_ERR(drvdata->sysc)) {
         drvdata->sysc =
syscon_regmap_lookup_by_compatible("mediatek,mt7621-sysc");
         if (IS_ERR(drvdata->sysc))
              return PTR_ERR(drvdata->sysc);
}

....

So in that case, we can add the new phandle to the bindings without
any kind of ABI breakage and we can use old dtbs using new watchdog
driver code.

I really hope I finally understood this properly. Thanks for your
patience, Krzysztof.

Best regards,
    Sergio Paracuellos

Best regards,
Krzysztof