[PATCH 1/2] drm/aspeed: Look up syscon by phandle

On Tue, 2 Feb 2021 at 04:39, Jeremy Kerr [off-list ref] wrote:

Hi Joel,

Sounds like a good idea! One comment though:

quoted

@@ -111,10 +112,13 @@ static int aspeed_gfx_load(struct drm_device *drm)
        if (IS_ERR(priv->base))
                return PTR_ERR(priv->base);

-       priv->scu = syscon_regmap_lookup_by_compatible("aspeed,ast2500-scu");
+       priv->scu = syscon_regmap_lookup_by_phandle(np, "syscon");
        if (IS_ERR(priv->scu)) {
-               dev_err(&pdev->dev, "failed to find SCU regmap\n");
-               return PTR_ERR(priv->scu);
+               priv->scu = syscon_regmap_lookup_by_compatible("aspeed,aspeed-scu");

Is this (more generic) compatible value guaranteed to exist alongside
aspeed,ast2500-scu? The scu binding only specifies the model-specific
ones:

    Documentation/devicetree/bindings/mfd/aspeed-scu.txt:

    Required properties:
    - compatible:       One of:
                    "aspeed,ast2400-scu", "syscon", "simple-mfd"
                    "aspeed,ast2500-scu", "syscon", "simple-mfd"

- the only mention of the new compatible value that I can find is this
thread. Maybe we should retain the existing one to keep the fallback
case working?

Yes, it was a mistake to change ast2500-scu to aspeed-scu. The only
reason to keep the lookup_by_compatible was to decouple this patch
from the device tree changes.

I will send a v2 with syscon_regmap_lookup_by_compatible("aspeed,ast2500-scu").