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Subject[PATCH v2 0/6] hwspinlock: allow sharing of hwspinlocks
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The current implementation does not allow two different devices to use
a common hwspinlock. This patch set proposes to have, as an option, some
hwspinlocks shared between several users.

Below is an example that explain the need for this:
exti: interrupt-controller@5000d000 {
compatible = "st,stm32mp1-exti", "syscon";
interrupt-controller;
#interrupt-cells = <2>;
reg = <0x5000d000 0x400>;
hwlocks = <&hsem 1>;
};
The two drivers (stm32mp1-exti and syscon) refer to the same hwlock.
With the current hwspinlock implementation, only the first driver succeeds
in requesting (hwspin_lock_request_specific) the hwlock. The second request
fails.


The proposed approach does not modify the API, but extends the DT 'hwlocks'
property with a second optional parameter (the first one identifies an
hwlock) that specifies whether an hwlock is requested for exclusive usage
(current behavior) or can be shared between several users.
Examples:
hwlocks = <&hsem 8>; Ref to hwlock #8 for exclusive usage
hwlocks = <&hsem 8 0>; Ref to hwlock #8 for exclusive (0) usage
hwlocks = <&hsem 8 1>; Ref to hwlock #8 for shared (1) usage

As a constraint, the #hwlock-cells value must be 1 or 2.
In the current implementation, this can have theorically any value but:
- all of the exisiting drivers use the same value : 1.
- the framework supports only one value : 1 (see implementation of
of_hwspin_lock_simple_xlate())
Hence, it shall not be a problem to restrict this value to 1 or 2 since
it won't break any driver.

Changes since v1:
* Removed useless 'status = "okay"' from stm32mp157c.dtsi

Fabien Dessenne (6):
dt-bindings: hwlock: add support of shared locks
hwspinlock: allow sharing of hwspinlocks
dt-bindings: hwlock: update STM32 #hwlock-cells value
ARM: dts: stm32: Add hwspinlock node for stm32mp157 SoC
ARM: dts: stm32: Add hwlock for irqchip on stm32mp157
ARM: dts: stm32: hwlocks for GPIO for stm32mp157

.../devicetree/bindings/hwlock/hwlock.txt | 27 +++++--
.../bindings/hwlock/st,stm32-hwspinlock.txt | 6 +-
Documentation/hwspinlock.txt | 10 ++-
arch/arm/boot/dts/stm32mp157-pinctrl.dtsi | 2 +
arch/arm/boot/dts/stm32mp157c.dtsi | 9 +++
drivers/hwspinlock/hwspinlock_core.c | 82 +++++++++++++++++-----
drivers/hwspinlock/hwspinlock_internal.h | 2 +
7 files changed, 107 insertions(+), 31 deletions(-)

--
2.7.4

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