| Message ID | 20241211-syscon-fixes-v1-3-b5ac8c219e96@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mfd: syscon: Cleanup, fix race condition and remove platform driver | expand |
Hi Rob, Thanks for working on this! On 12/11/2024, 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> > --- > drivers/mfd/syscon.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c > index bfb1f69fcff1..e6df2825c14d 100644 > --- a/drivers/mfd/syscon.c > +++ b/drivers/mfd/syscon.c > @@ -171,8 +171,10 @@ static struct regmap *device_node_get_regmap(struct device_node *np, > break; > } > > - if (!syscon) > + if (!syscon && of_device_is_compatible(np, "syscon")) > syscon = of_syscon_register(np, check_res); > + else > + syscon = ERR_PTR(-EINVAL); This else case actually breaks Pixel 6 (Tensor) since you are now returning -EINVAL when the syscon is created by the exynos-pmu driver and present in the list. Instead you should only return -EINVAL if the syscon doesn't exist and the device node is not a compatible syscon device. If you still want to check for `of_device_is_compatible(np, "syscon")` even when the syscon is found in the list, that should be okay , but it's probably best to check that before inserting the regmap in the list to begin with. This worked for me on my Pixel 6 device: if (!syscon) { if (of_device_is_compatible(np, "syscon")) syscon = of_syscon_register(np, check_res); else syscon = ERR_PTR(-EINVAL); } Thanks, Will
diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c index bfb1f69fcff1..e6df2825c14d 100644 --- a/drivers/mfd/syscon.c +++ b/drivers/mfd/syscon.c @@ -171,8 +171,10 @@ static struct regmap *device_node_get_regmap(struct device_node *np, break; } - if (!syscon) + if (!syscon && of_device_is_compatible(np, "syscon")) syscon = of_syscon_register(np, check_res); + else + syscon = ERR_PTR(-EINVAL); mutex_unlock(&syscon_list_lock); @@ -238,9 +240,6 @@ 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> --- drivers/mfd/syscon.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)