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* [PATCH v2 0/6] hwspinlock: allow sharing of hwspinlocks
@ 2019-04-25  9:17 Fabien Dessenne
  2019-04-25  9:17 ` [PATCH v2 1/6] dt-bindings: hwlock: add support of shared locks Fabien Dessenne
                   ` (6 more replies)
  0 siblings, 7 replies; 8+ messages in thread
From: Fabien Dessenne @ 2019-04-25  9:17 UTC (permalink / raw)
  To: Ohad Ben-Cohen, Bjorn Andersson, Rob Herring, Mark Rutland,
	Maxime Coquelin, Alexandre Torgue, Jonathan Corbet,
	linux-remoteproc, devicetree, linux-kernel, linux-stm32,
	linux-arm-kernel, linux-doc
  Cc: Fabien Dessenne, Benjamin Gaignard

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


^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2019-05-13  9:14 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-04-25  9:17 [PATCH v2 0/6] hwspinlock: allow sharing of hwspinlocks Fabien Dessenne
2019-04-25  9:17 ` [PATCH v2 1/6] dt-bindings: hwlock: add support of shared locks Fabien Dessenne
2019-04-25  9:17 ` [PATCH v2 2/6] hwspinlock: allow sharing of hwspinlocks Fabien Dessenne
2019-04-25  9:17 ` [PATCH v2 3/6] dt-bindings: hwlock: update STM32 #hwlock-cells value Fabien Dessenne
2019-04-25  9:17 ` [PATCH v2 4/6] ARM: dts: stm32: Add hwspinlock node for stm32mp157 SoC Fabien Dessenne
2019-04-25  9:17 ` [PATCH v2 5/6] ARM: dts: stm32: Add hwlock for irqchip on stm32mp157 Fabien Dessenne
2019-04-25  9:17 ` [PATCH v2 6/6] ARM: dts: stm32: hwlocks for GPIO for stm32mp157 Fabien Dessenne
2019-05-13  9:13 ` [PATCH v2 0/6] hwspinlock: allow sharing of hwspinlocks Fabien DESSENNE

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