| Message ID | 20220517235919.200375-2-marex@denx.de (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | [v3,1/2] dt-bindings: clk: Introduce 'critical-clocks' property | expand |
Quoting Marek Vasut (2022-05-17 16:59:19) > Some platforms require select clock to be always running, e.g. because > those clock supply vital devices which are not otherwise attached to > the system and thus do not have a matching DT node and clock consumer. > > An example is a system where the SoC serves as a crystal oscillator > replacement for a programmable logic device. The "critical-clocks" > property of a clock controller allows listing clock which must never > be turned off. > > Clock listed in the "critical-clocks" property may have other consumers > in DT, listing the clock in "critical-clocks" only assures those clock > are never turned off, and none of these optional additional consumers > can turn the clock off either. This is achieved by adding CLK_IS_CRITICAL > flag to these critical clock. > > This flag has thus far been added to select clock by hard-coding it in > various clock drivers, this patch provides generic DT interface to add > the flag to arbitrary clock that may be critical. > > The implementation is modeled after "protected-clocks", except the protected > clock property is currently driver specific. This patch attempts to provide > a generic implementation of "critical-clocks" instead. > > Unlike "assigned-clocks", the "critical-clocks" must be parsed much earlier > in __clk_register() to assign CLK_IS_CRITICAL flag to clk_init_data .flags > field. Why? Instead of using the CLK_IS_CRITICAL flag to enable at registration time for this, why can't we parse the property when a clk provider is registered and enable those clks manually and then set the CLK_IS_CRITICAL flag? Ideally we don't implement another clk_op for this. > > 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-clocks" property, and if so, then the CLK_IS_CRITICAL is added to > these newly registered clock. This callback can only be driver specific. > > Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index f00d4c1158d72..e04bca5e1ff30 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -3902,6 +3902,48 @@ static void clk_core_free_parent_map(struct clk_core *core) kfree(core->parents); } +static void +__clk_register_critical_clock(struct clk_core *core, struct clk_hw *hw) +{ + struct device_node *np = core->of_node; + struct of_phandle_args clkspec; + u32 clksize, clktotal; + int ret, i, index; + + if (!np) + return; + + if (of_property_read_u32(np, "#clock-cells", &clksize)) + return; + + /* Clock node with #clock-cells = <0> uses critical-clocks; */ + if (clksize == 0) { + if (of_property_read_bool(np, "critical-clocks")) + core->flags |= CLK_IS_CRITICAL; + return; + } + + if (!core->ops->match_clkspec) + return; + + 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 (ret) { + pr_warn("Skipping critical-clocks index %d (ret=%d)\n", + i, ret); + } + } + if (!core->ops->match_clkspec(hw, &clkspec)) + core->flags |= CLK_IS_CRITICAL; + } +} + static struct clk * __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw) { @@ -3946,6 +3988,8 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw) core->min_rate = 0; core->max_rate = ULONG_MAX; + __clk_register_critical_clock(core, hw); + 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 c10dc4c659e23..f65f6ef4e9985 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -205,6 +205,8 @@ 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. + * Returns 0 on success, -EERROR otherwise. * * The clk_enable/clk_disable and clk_prepare/clk_unprepare pairs allow * implementations to split any work between atomic (enable) and sleepable @@ -252,6 +254,7 @@ 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); }; /**
Some platforms require select clock to be always running, e.g. because those clock supply vital devices which are not otherwise attached to the system and thus do not have a matching DT node and clock consumer. An example is a system where the SoC serves as a crystal oscillator replacement for a programmable logic device. The "critical-clocks" property of a clock controller allows listing clock which must never be turned off. Clock listed in the "critical-clocks" property may have other consumers in DT, listing the clock in "critical-clocks" only assures those clock are never turned off, and none of these optional additional consumers can turn the clock off either. This is achieved by adding CLK_IS_CRITICAL flag to these critical clock. This flag has thus far been added to select clock by hard-coding it in various clock drivers, this patch provides generic DT interface to add the flag to arbitrary clock that may be critical. The implementation is modeled after "protected-clocks", except the protected clock property is currently driver specific. This patch attempts to provide a generic implementation of "critical-clocks" instead. Unlike "assigned-clocks", the "critical-clocks" must be parsed much earlier in __clk_register() to assign CLK_IS_CRITICAL flag to clk_init_data .flags field. 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-clocks" property, and if so, then the CLK_IS_CRITICAL is added to these newly registered clock. This callback can only be driver specific. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Michael Turquette <mturquette@baylibre.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: Stephen Boyd <sboyd@kernel.org> Cc: devicetree@vger.kernel.org To: linux-clk@vger.kernel.org --- V2: - Warn in case critical-clock field cannot be parsed and skip those clock - Use match_clkspec() only for non-zero clock-cells controllers - Pull the critical-clock code into __clk_register_critical_clock() - Update commit message V3: - Pick np from clk_core->of_node --- drivers/clk/clk.c | 44 ++++++++++++++++++++++++++++++++++++ include/linux/clk-provider.h | 3 +++ 2 files changed, 47 insertions(+)