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SubjectRe: [PATCH v2] of: base: Skip CPU nodes with "fail"/"fail-..." status
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On 11/22/2021 5:15 PM, Matthias Schiffer wrote:
> Allow fully disabling CPU nodes using status = "fail".
>
> 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.
>
> Unknown status values (everything that is not "okay"/"ok", "disabled" or
> "fail"/"fail-...") will continue to be interpreted like "disabled",
> meaning that the CPU can be enabled during boot.
>
> 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>
> ---
>
> v2: Treat unknown status values like "disabled", not like "fail"
>
>
> drivers/of/base.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 61de453b885c..5b907600f5b0 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -650,6 +650,28 @@ bool of_device_is_available(const struct device_node *device)
> }
> EXPORT_SYMBOL(of_device_is_available);
>
> +/**
> + * __of_device_is_fail - check if a device has status "fail" or "fail-..."
> + *
> + * @device: Node to check status for, with locks already held
> + *
> + * Return: True if the status property is set to "fail" or "fail-..." (for any
> + * error code suffix), false otherwise
> + */
> +static bool __of_device_is_fail(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, "fail") || !strncmp(status, "fail-", 5);
> +}
> +
> /**
> * of_device_is_big_endian - check if a device has BE registers
> *
> @@ -796,6 +818,9 @@ EXPORT_SYMBOL(of_get_next_available_child);
> * of_get_next_cpu_node - Iterate on cpu nodes
> * @prev: previous child of the /cpus node, or NULL to get first
> *
> + * Unusable CPUs (those with the status property set to "fail" or "fail-...")
> + * will be skipped.
> + *
> * Return: A cpu node pointer with refcount incremented, use of_node_put()
> * on it when done. Returns NULL when prev is the last child. Decrements
> * the refcount of prev.
> @@ -817,6 +842,8 @@ 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_fail(next))
> + continue;
> if (!(of_node_name_eq(next, "cpu") ||
> __of_node_is_type(next, "cpu")))
> continue;

Thanks for the patch, we have a similar usecase coming up and this is
very useful than fixing up phandles.

Tested-by: Sai Prakash Ranjan <quic_saipraka@quicinc.com>

-Sai

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