From 6f73b7f399440eee282d746b1907e28f45b81a14 Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Mon, 8 Nov 2021 23:42:42 +0100 Subject: [PATCH] dt-bindings: clk: Introduce 'critical-clocks' property NOTE: This is an RFC patch showing how this mechanism might be workable. Some platforms require clock to be always running, e.g. because those clock supply devices which are not otherwise attached to the system. One example is a system where the SoC serves as a crystal oscillator replacement for a programmable logic device. The critical-clock property of a clock controller allows listing clock which must never be turned off. The implementation here is similar to "protected-clock", except protected clock property is currently driver specific. This patch attempts to make a generic implementation of "critical-clock" instead. Unlike "assigned-clocks", the "critical-clock" must be parsed much earlier in __clk_register() to assign CLK_IS_CRITICAL flag to clk_init_data .flags field. The parsing code obviously need to be cleaned up and factor out into separate function. The new match_clkspec() callback is used to determine whether struct clk_hw that is currently being registered matches the clock specifier in the DT "critical-clock" property, and if so, then the CLK_IS_CRITICAL is added to these newly registered clock. This callback is currently driver specific, although I suspect a common and/or generic version of the callback could be added. Also, this new callback could possibly be used to replace (*get) argument of of_clk_add_hw_provider() later on too. Thoughts (on the overall design, not code quality or patch splitting) ? Signed-off-by: Marek Vasut Cc: Matti Vaittinen Cc: Michael Turquette Cc: Rob Herring Cc: Stephen Boyd Cc: devicetree@vger.kernel.org Cc: linux-power@fi.rohmeurope.com To: linux-clk@vger.kernel.org --- .../bindings/clock/clock-bindings.txt | 16 ++++++++++++ drivers/clk/clk-bd718x7.c | 15 +++++++++++ drivers/clk/clk.c | 25 +++++++++++++++++++ include/linux/clk-provider.h | 2 ++ 4 files changed, 58 insertions(+) diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt index f2ea53832ac63e..d9a783c35c5a1f 100644 --- a/Documentation/devicetree/bindings/clock/clock-bindings.txt +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt @@ -169,6 +169,22 @@ a shared clock is forbidden. Configuration of common clocks, which affect multiple consumer devices can be similarly specified in the clock provider node. +==Critical clocks== + +Some platforms require clock to be always running, e.g. because those clock +supply devices which are not otherwise attached to the system. One example +is a system where the SoC serves as a crystal oscillator replacement for a +programmable logic device. The critical-clock property of a clock controller +allows listing clock which must never be turned off. + + clock-controller@a000f000 { + compatible = "vendor,clk95; + reg = <0xa000f000 0x1000> + #clocks-cells = <1>; + ... + critical-clocks = , ; + }; + ==Protected clocks== Some platforms or firmwares may not fully expose all the clocks to the OS, such diff --git a/drivers/clk/clk-bd718x7.c b/drivers/clk/clk-bd718x7.c index ac40b669d60b74..90b81a35f503f9 100644 --- a/drivers/clk/clk-bd718x7.c +++ b/drivers/clk/clk-bd718x7.c @@ -70,10 +70,25 @@ static int bd71837_clk_is_enabled(struct clk_hw *hw) return enabled & c->mask; } +static int bd71837_match_clkspec(struct clk_hw *hw, struct of_phandle_args *clkspec) +{ + struct bd718xx_clk *c = container_of(hw, struct bd718xx_clk, hw); + + /* + * if (clk_hw == clkspec) + * return 0; + * else + * return 1; + */ + + return 0; +} + static const struct clk_ops bd71837_clk_ops = { .prepare = &bd71837_clk_enable, .unprepare = &bd71837_clk_disable, .is_prepared = &bd71837_clk_is_enabled, + .match_clkspec = &bd71837_match_clkspec, }; static int bd71837_clk_probe(struct platform_device *pdev) diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index f467d63bbf1eef..fa8e9ea446158f 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -3849,6 +3849,31 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw) core->max_rate = ULONG_MAX; hw->core = core; + struct of_phandle_args clkspec; + u32 clksize, clktotal; + int i, index; + + if (np && core->ops->match_clkspec && !of_property_read_u32(np, "#clock-cells", &clksize)) { + if (clksize == 0) { + if (of_property_read_bool(np, "critical-clocks")) + core->flags |= CLK_IS_CRITICAL; + clktotal = 0; + } else { + clkspec.np = np; + clktotal = of_property_count_u32_elems(np, "critical-clocks"); + clktotal /= clksize; + for (index = 0; index < clktotal; index++) { + for (i = 0; i < clksize; i++) { + ret = of_property_read_u32_index(np, "critical-clocks", + (index * clksize) + i, + &(clkspec.args[i])); + } + if (!core->ops->match_clkspec(hw, &clkspec)) + core->flags |= CLK_IS_CRITICAL; + } + } + } + ret = clk_core_populate_parent_map(core, init); if (ret) goto fail_parents; diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index f59c875271a0ee..766e93efb23c55 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -205,6 +205,7 @@ struct clk_duty { * directory is provided as an argument. Called with * prepare_lock held. Returns 0 on success, -EERROR otherwise. * + * @match_clkspec: Check whether clk_hw matches DT clock specifier * * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow * implementations to split any work between atomic (enable) and sleepable @@ -252,6 +253,7 @@ struct clk_ops { int (*init)(struct clk_hw *hw); void (*terminate)(struct clk_hw *hw); void (*debug_init)(struct clk_hw *hw, struct dentry *dentry); + int (*match_clkspec)(struct clk_hw *hw, struct of_phandle_args *clkspec); }; /**