| Message ID | 20241217-syscon-fixes-v2-3-4f56d750541d@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mfd: syscon: Cleanup, fix race condition and remove platform driver | expand |
On 12/17/2024, Rob Herring (Arm) wrote: > of_syscon_register_regmap() was added for nodes which need a custom > regmap setup. It's not really correct for those nodes to claim they are > compatible with "syscon" as the default handling likely doesn't work in > those cases. If device_node_get_regmap() happens to be called first, > then of_syscon_register() will be called and an incorrect regmap will be > created (barring some other error). That may lead to unknown results in > the worst case. In the best case, of_syscon_register_regmap() will fail > with -EEXIST. This problem remains unless these cases drop "syscon" (an > ABI issue) or we exclude them using their specific compatible. ATM, > there is only one user: "google,gs101-pmu" > > There are also cases of adding "syscon" compatible to existing nodes > after the fact in order to register the syscon. That presents a > potential DT ABI problem. Instead, if there's a kernel change needing a > syscon for a node, then it should be possible to allow the kernel to > register a syscon without a DT change. That's only possible by using > of_syscon_register_regmap() currently, but in the future we may want to > support a match list for cases which don't need a custom regmap. > > With this change, the lookup functions will succeed for any node > registered by of_syscon_register_regmap() regardless of whether the node > compatible contains "syscon". > > Signed-off-by: Rob Herring (Arm) <robh@kernel.org> I verified this works on my Pixel 6. Thanks! Tested-by: Will McVicker <willmcvicker@google.com> Thanks, Will
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c index bfb1f69fcff1d3cd35cf04ccd4c449e7d0395c79..226915ca3c93dcaf47bdd46b58e00e10e155f952 100644 --- a/drivers/mfd/syscon.c +++ b/drivers/mfd/syscon.c @@ -171,9 +171,12 @@ static struct regmap *device_node_get_regmap(struct device_node *np, break; } - if (!syscon) - syscon = of_syscon_register(np, check_res); - + if (!syscon) { + if (of_device_is_compatible(np, "syscon")) + syscon = of_syscon_register(np, check_res); + else + syscon = ERR_PTR(-EINVAL); + } mutex_unlock(&syscon_list_lock); if (IS_ERR(syscon)) @@ -238,9 +241,6 @@ EXPORT_SYMBOL_GPL(device_node_to_regmap); struct regmap *syscon_node_to_regmap(struct device_node *np) { - if (!of_device_is_compatible(np, "syscon")) - return ERR_PTR(-EINVAL); - return device_node_get_regmap(np, true); } EXPORT_SYMBOL_GPL(syscon_node_to_regmap);
of_syscon_register_regmap() was added for nodes which need a custom regmap setup. It's not really correct for those nodes to claim they are compatible with "syscon" as the default handling likely doesn't work in those cases. If device_node_get_regmap() happens to be called first, then of_syscon_register() will be called and an incorrect regmap will be created (barring some other error). That may lead to unknown results in the worst case. In the best case, of_syscon_register_regmap() will fail with -EEXIST. This problem remains unless these cases drop "syscon" (an ABI issue) or we exclude them using their specific compatible. ATM, there is only one user: "google,gs101-pmu" There are also cases of adding "syscon" compatible to existing nodes after the fact in order to register the syscon. That presents a potential DT ABI problem. Instead, if there's a kernel change needing a syscon for a node, then it should be possible to allow the kernel to register a syscon without a DT change. That's only possible by using of_syscon_register_regmap() currently, but in the future we may want to support a match list for cases which don't need a custom regmap. With this change, the lookup functions will succeed for any node registered by of_syscon_register_regmap() regardless of whether the node compatible contains "syscon". Signed-off-by: Rob Herring (Arm) <robh@kernel.org> --- v2: - Fix logic when a syscon is found in list to not return an error --- drivers/mfd/syscon.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)