Re: [PATCH v7 1/8] of/platform: Allow overlays to create platform devices from the root node

[Geert Uytterhoeven]

Hi Stephen,

On Wed, Jul 10, 2024 at 10:14 PM Stephen Boyd <sboyd@xxxxxxxxxx> wrote:
> We'd like to apply overlays to the root node in KUnit so we can test
> platform devices created as children of the root node.
>
> On some architectures (powerpc), the root node isn't marked with
> OF_POPULATED_BUS. If an overlay tries to modify the root node on these
> platforms it will fail, while on other platforms, such as ARM, it will
> succeed. This is because the root node is marked with OF_POPULATED_BUS
> by of_platform_default_populate_init() calling
> of_platform_default_populate() with NULL as the first argument.
>
> Loosen the requirement here so that platform devices can be created for
> nodes created as children of the root node via DT overlays even if the
> platform bus wasn't populated for the root node.
>
> Reviewed-by: Rob Herring (Arm) <robh@xxxxxxxxxx>
> Cc: Saravana Kannan <saravanak@xxxxxxxxxx>
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxx>

Thanks for your patch, which is now commit 98290f295fbcf18f
("of/platform: Allow overlays to create platform devices from the
root node") in clk/clk-next.

This causes i2c-demux-pinctrl to fail on the Koelsch development board:

        i2c-demux-pinctrl i2c-mux1: failed to setup demux-adapter 0 (-19)
        i2c-demux-pinctrl i2c-mux2: failed to setup demux-adapter 0 (-19)
        i2c-demux-pinctrl i2c-mux3: failed to setup demux-adapter 0 (-19)
        i2c-demux-pinctrl i2c-mux2: Failed to create device link
(0x180) with e6ef0000.video
        i2c-demux-pinctrl i2c-mux2: Failed to create device link
(0x180) with e6ef1000.video
        i2c-demux-pinctrl i2c-mux2: Failed to create device link
(0x180) with hdmi-in
        i2c-demux-pinctrl i2c-mux2: Failed to create device link
(0x180) with hdmi-out

and anything relying on I2C connected to these muxes fails, too.

Also, loading the 25LC040 DT overlay[1] on Ebisu using the out-of-tree
of-configfs now fails, too.

> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -732,11 +732,14 @@ static int of_platform_notify(struct notifier_block *nb,
>         struct of_reconfig_data *rd = arg;
>         struct platform_device *pdev_parent, *pdev;
>         bool children_left;
> +       struct device_node *parent;
>
>         switch (of_reconfig_get_state_change(action, rd)) {
>         case OF_RECONFIG_CHANGE_ADD:
> -               /* verify that the parent is a bus */
> -               if (!of_node_check_flag(rd->dn->parent, OF_POPULATED_BUS))
> +               parent = rd->dn->parent;
> +               /* verify that the parent is a bus (or the root node) */
> +               if (!of_node_is_root(parent) &&

Parent = /soc, so this returns early. Hence of_changeset_apply() [2]
didn't add the I2C mux bus, causing of_get_i2c_adapter_by_node() [3]
to fail.

> +                   of_node_check_flag(parent, OF_POPULATED_BUS))

Oh, you inverted the check for of_node_check_flag(); was that
intentional?  Re-adding the "!" fixes all issues for me.

>                         return NOTIFY_OK;       /* not for us */
>
>                 /* already populated? (driver using of_populate manually) */
> @@ -749,7 +752,7 @@ static int of_platform_notify(struct notifier_block *nb,
>                  */
>                 rd->dn->fwnode.flags &= ~FWNODE_FLAG_NOT_DEVICE;
>                 /* pdev_parent may be NULL when no bus platform device */
> -               pdev_parent = of_find_device_by_node(rd->dn->parent);
> +               pdev_parent = of_find_device_by_node(parent);
>                 pdev = of_platform_device_create(rd->dn, NULL,
>                                 pdev_parent ? &pdev_parent->dev : NULL);
>                 platform_device_put(pdev_parent);

[1] https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/tree/arch/arm64/boot/dts/renesas/r8a77990-ebisu-cn41-msiof0-25lc040.dtso?h=topic/renesas-overlays
[2] https://elixir.bootlin.com/linux/latest/source/drivers/i2c/muxes/i2c-demux-pinctrl.c#L60
[3] https://elixir.bootlin.com/linux/latest/source/drivers/i2c/muxes/i2c-demux-pinctrl.c#L64

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds