linux-stable.git/drivers/mfd/syscon.c, branch v6.14

mfd: syscon: Restore device_node_to_regmap() for non-syscon nodes

2025-02-11T14:53:39+00:00

Commit ba5095ebbc7a ("mfd: syscon: Allow syscon nodes without a
"syscon" compatible") broke drivers which call device_node_to_regmap()
on nodes without a "syscon" compatible. Restore the prior behavior for
device_node_to_regmap().

This also makes using device_node_to_regmap() incompatible with
of_syscon_register_regmap() again, so add kerneldoc for
device_node_to_regmap() and syscon_node_to_regmap() to make it clear
how and when each one should be used.

Fixes: ba5095ebbc7a ("mfd: syscon: Allow syscon nodes without a "syscon" compatible")
Reported-by: Vaishnav Achath 
Signed-off-by: Rob Herring (Arm) 
Reviewed-by: Daniel Golle 
Reviewed-by: AngeloGioacchino Del Regno 
Tested-by: Chen-Yu Tsai 
Tested-by: Nishanth Menon 
Tested-by: Daniel Golle 
Tested-by: Frank Wunderlich 
Tested-by: Dhruva Gole 
Tested-by: Nícolas F. R. A. Prado 
Tested-by: AngeloGioacchino Del Regno 
Link: https://lore.kernel.org/r/20250124191644.2309790-1-robh@kernel.org
Signed-off-by: Lee Jones

mfd: syscon: Allow syscon nodes without a "syscon" compatible

2025-01-09T11:11:54+00:00

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) 
Tested-by: Will McVicker 
Reviewed-by: Pankaj Dubey 
Reviewed-by: Krzysztof Kozlowski 
Link: https://lore.kernel.org/r/20241217-syscon-fixes-v2-3-4f56d750541d@kernel.org
Signed-off-by: Lee Jones

mfd: syscon: Remove the platform driver support

2025-01-09T11:11:47+00:00

The platform driver is dead code. It is not used by DT platforms since
commit bdb0066df96e ("mfd: syscon: Decouple syscon interface from
platform devices") which said:

    For non-DT based platforms, this patch keeps syscon platform driver
    structure so that syscon can be probed and such non-DT based drivers
    can use syscon_regmap_lookup_by_pdev API and access regmap handles.
    Once all users of "syscon_regmap_lookup_by_pdev" migrated to DT based,
    we can completely remove platform driver of syscon, and keep only helper
    functions to get regmap handles.

The last user of syscon_regmap_lookup_by_pdevname() was removed in 2018.
syscon_regmap_lookup_by_pdevname() was then removed in 2019, but that
commit failed to remove the rest of the platform driver.

Signed-off-by: Rob Herring (Arm) 
Tested-by: Krzysztof Kozlowski 
Tested-by: Will McVicker 
Acked-by: Liviu Dudau 
Reviewed-by: Pankaj Dubey 
Tested-by: Pankaj Dubey 
Reviewed-by: Krzysztof Kozlowski 
Link: https://lore.kernel.org/r/20241217-syscon-fixes-v2-2-4f56d750541d@kernel.org
Signed-off-by: Lee Jones

mfd: syscon: Fix race in device_node_get_regmap()

2025-01-09T11:11:36+00:00

It is possible for multiple, simultaneous callers calling
device_node_get_regmap() with the same node to fail to find an entry in
the syscon_list. There is a period of time while the first caller is
calling of_syscon_register() that subsequent callers also fail to find
an entry in the syscon_list and then call of_syscon_register() a second
time.

Fix this by keeping the lock held until after of_syscon_register()
completes and adds the node to syscon_list. Convert the spinlock to a
mutex as many of the functions called in of_syscon_register() such as
kzalloc() and of_clk_get() may sleep.

Fixes: bdb0066df96e ("mfd: syscon: Decouple syscon interface from platform devices")
Signed-off-by: Rob Herring (Arm) 
Reviewed-by: Krzysztof Kozlowski 
Tested-by: Krzysztof Kozlowski 
Tested-by: Will McVicker 
Tested-by: Pankaj Dubey 
Reviewed-by: Pankaj Dubey 
Link: https://lore.kernel.org/r/20241217-syscon-fixes-v2-1-4f56d750541d@kernel.org
Signed-off-by: Lee Jones

mfd: syscon: Use regmap max_register_is_0 as needed

2024-10-16T08:04:09+00:00

syscon has always set the optional max_register configuration of
regmap to ensure the correct checks are in place. However, a recent
commit 0ec74ad3c157 ("regmap: rework ->max_register handling")
introduced explicit configuration in regmap framework for register
maps that is exactly 1 register, when max_register is pointing to a
valid register 0. This commit solved a previous limitation of regmap
framework.

Update syscon driver to consistent in regmap configuration for
all sizes of syscons by using this new capability by setting
max_register_is_0, when the max_register is valid and 0.

Signed-off-by: Nishanth Menon 
Link: https://lore.kernel.org/r/20240903184710.1552067-1-nm@ti.com
Signed-off-by: Lee Jones

mfd: syscon: Use scoped variables with memory allocators to simplify error paths

2024-08-30T08:40:13+00:00

Allocate the memory with scoped/cleanup.h to reduce error handling and
make the code a bit simpler.

Signed-off-by: Krzysztof Kozlowski 
Link: https://lore.kernel.org/r/20240707114823.9175-2-krzysztof.kozlowski@linaro.org
Signed-off-by: Lee Jones

mfd: syscon: Add of_syscon_register_regmap() API

2024-06-26T15:46:50+00:00

The of_syscon_register_regmap() API allows an externally created regmap
to be registered with syscon. This regmap can then be returned to client
drivers using the syscon_regmap_lookup_by_phandle() APIs.

The API is used by platforms where mmio access to the syscon registers is
not possible, and a underlying soc driver like exynos-pmu provides a SoC
specific regmap that can issue a SMC or hypervisor call to write the
register.

This approach keeps the SoC complexities out of syscon, but allows common
drivers such as  syscon-poweroff, syscon-reboot and friends that are used
by many SoCs already to be re-used.

Signed-off-by: Peter Griffin 
Reviewed-by: Arnd Bergmann 
Reviewed-by: Sam Protsenko 
Tested-by: Will McVicker 
Reviewed-by: Krzysztof Kozlowski 
Link: https://lore.kernel.org/r/20240621115544.1655458-2-peter.griffin@linaro.org
Signed-off-by: Lee Jones

mfd: syscon: Call of_node_put() only when of_parse_phandle() takes a ref

2024-02-23T16:02:02+00:00

of_parse_phandle() returns a device_node with refcount incremented, which
the callee needs to call of_node_put() on when done. We should only call
of_node_put() when the property argument is provided though as otherwise
nothing has taken a reference on the node.

Fixes: 45330bb43421 ("mfd: syscon: Allow property as NULL in syscon_regmap_lookup_by_phandle")
Signed-off-by: Peter Griffin 
Link: https://lore.kernel.org/r/20240220115012.471689-2-peter.griffin@linaro.org
Signed-off-by: Lee Jones

mfd: syscon: Fix null pointer dereference in of_syscon_register()

2023-12-07T16:05:11+00:00

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure.

Fixes: e15d7f2b81d2 ("mfd: syscon: Use a unique name with regmap_config")
Signed-off-by: Kunwu Chan 
Reviewed-by: Arnd Bergmann 
Link: https://lore.kernel.org/r/20231204092443.2462115-1-chentao@kylinos.cn
Signed-off-by: Lee Jones

mfd: syscon: Allow reset control for syscon devices

2023-02-22T08:25:53+00:00

Simple syscon devices may require deassertion of a reset signal in order
to access their register set. Rather than requiring a custom driver to
implement this, we can use the generic "resets" specifiers to link a
reset line to the syscon.

This change adds an optional reset line to the syscon device
description, and deasserts the reset if detected.

Signed-off-by: Jeremy Kerr 
Reviewed-by: Arnd Bergmann 
Signed-off-by: Lee Jones 
Link: https://lore.kernel.org/r/20230105005010.124948-3-jk@codeconstruct.com.au