On Sun, 2021-11-14 at 14:41 -0500, Frank Rowand wrote: > 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@xxxxxxxxxxxxxxx> > > --- > > 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. Previously, there were two option for the (effective) value of the status of a device_node: - "okay", "ok" or unset - anything else (which includes "disabled" and "fail") __of_device_is_available() checks which of these two is the case. With the new code, we have 3 cases for the status of CPU nodes: - "okay", "ok" or unset - "disabled" - anything else ("fail", ...) My patch will only change the behaviour in one case: When a CPU node has a status that is not "okay", "ok", "disabled" or unset - which is exactly the point of my patch. See also the change [1], which removed the !available check a while ago, and the discussion in [2], which led us to the conclusion that of_get_next_cpu_node() must not distinguish "okay" and "disabled" CPU nodes and we instead need a third status to disable a CPU for real. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/of/base.c?id=c961cb3be9064d1097ccc019390f8b5739daafc6 [2] https://www.lkml.org/lkml/2020/8/26/1237 > > -Frank > > > + continue; > > if (!(of_node_name_eq(next, "cpu") || > > __of_node_is_type(next, "cpu"))) > > continue; > > > >
