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SubjectRe: [PATCH] of: base: Skip CPU nodes with non-"okay"/"disabled" status
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On 11/8/21 3:48 AM, Matthias Schiffer wrote:
> Allow fully disabling CPU nodes using status = "fail". Having no status
> property at all is still interpreted as "okay" as usual.
>
> This allows a bootloader to change the number of available CPUs (for
> example when a common DTS is used for SoC variants with different numbers
> of cores) without deleting the nodes altogether, which could require
> additional fixups to avoid dangling phandle references.
>
> References:
> - https://www.lkml.org/lkml/2020/8/26/1237
> - https://www.spinics.net/lists/devicetree-spec/msg01007.html
> - https://github.com/devicetree-org/dt-schema/pull/61
>
> Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
> ---
> drivers/of/base.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 61de453b885c..4e9973627c8d 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -650,6 +650,32 @@ bool of_device_is_available(const struct device_node *device)
> }
> EXPORT_SYMBOL(of_device_is_available);
>
> +/**
> + * __of_device_is_disabled - check if a device has status "disabled"
> + *
> + * @device: Node to check status for, with locks already held
> + *
> + * Return: True if the status property is set to "disabled",
> + * false otherwise
> + *
> + * Most callers should use __of_device_is_available() instead, this function
> + * only exists due to the special interpretation of the "disabled" status for
> + * CPU nodes.
> + */
> +static bool __of_device_is_disabled(const struct device_node *device)
> +{
> + const char *status;
> +
> + if (!device)
> + return false;
> +
> + status = __of_get_property(device, "status", NULL);
> + if (status == NULL)
> + return false;
> +
> + return !strcmp(status, "disabled");
> +}
> +
> /**
> * of_device_is_big_endian - check if a device has BE registers
> *
> @@ -817,6 +843,9 @@ struct device_node *of_get_next_cpu_node(struct device_node *prev)
> of_node_put(node);
> }
> for (; next; next = next->sibling) {

> + if (!__of_device_is_available(next) &&
> + !__of_device_is_disabled(next))

Shouldn't that just be a check to continue if the device is disabled?

If adding a check for available, then all of the callers of for_each_of_cpu_node()
need to be checked. There is at least one that is suspicious - arch/arm/mach-imx/platsmp.c
has a comment:

* Initialise the CPU possible map early - this describes the CPUs
* which may be present or become present in the system.

-Frank

> + continue;
> if (!(of_node_name_eq(next, "cpu") ||
> __of_node_is_type(next, "cpu")))
> continue;
>

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