On Wed 13 Mar 08:50 PDT 2019, Fabien Dessenne wrote:
> 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.
>
Hi Fabien,
Your series looks good, but it makes me wonder why the hardware locks
should be an exclusive resource.
How about just making all (specific) locks shared?
Regards,
Bjorn
> 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 | 10 +++
> drivers/hwspinlock/hwspinlock_core.c | 82 +++++++++++++++++-----
> drivers/hwspinlock/hwspinlock_internal.h | 2 +
> 7 files changed, 108 insertions(+), 31 deletions(-)
>
> --
> 2.7.4
>
