| Message ID | 20220924174517.458657-1-marex@denx.de (mailing list archive) |
|---|---|
| State | Changes Requested, archived |
| Headers | show |
| Series | [v4] clk: Introduce 'always-on-clocks' property | expand |
Quoting Marek Vasut (2022-09-24 10:45:17) > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index b70769d0db99f..6b07f1a086277 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -3900,6 +3900,48 @@ 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 always-on-clocks; */ > + if (clksize == 0) { > + if (of_property_read_bool(np, "always-on-clocks")) > + core->flags |= CLK_IS_CRITICAL; Why must we set the CLK_IS_CRITICAL flag like this? Instead, when the clk provider is registered, parse the node of the provider and get the clks to call clk_prepare_enable() on. We can set the critical flag or make a new flag that causes clk_disable_unprepare() to not actually turn the clk off, if we have some sort of underflow issue with other consumers. Does that fail somehow? > + return; > + } > + > + if (!core->ops->match_clkspec) > + return; > + > + clkspec.np = np; > + clktotal = of_property_count_u32_elems(np, "always-on-clocks"); > + clktotal /= clksize; > + for (index = 0; index < clktotal; index++) { > + for (i = 0; i < clksize; i++) { I'm mainly thinking that we're going to spin on this loop constantly for any clk providers that have many clks to register, but only a few to keep always on. It would be best to avoid that and only run through the DT property once. > + ret = of_property_read_u32_index(np, "always-on-clocks", > + (index * clksize) + i, > + &(clkspec.args[i])); > + if (ret) { > + pr_warn("Skipping always-on-clocks index %d (ret=%d)\n", > + i, ret); > + } > + } > + if (!core->ops->match_clkspec(hw, &clkspec)) This callback is provider specific, and not necessarily clk_hw specific. For example, the clk_ops could be for a generic gate bit, but the provider wants to keep that gate always on. To implement such a clk we would have to copy the generic gate clk_ops and set this match_clkspec op. I'd like to avoid that if possible. If the clk_op must exist, then perhaps it should be in clk_init_data, which is sort of the place where we put provider specific information for a clk, i.e. clk_parent_data. > + core->flags |= CLK_IS_CRITICAL; > + } > +} > + > static struct clk * > __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw) > {
On 10/4/22 20:26, Stephen Boyd wrote: > Quoting Marek Vasut (2022-09-24 10:45:17) >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index b70769d0db99f..6b07f1a086277 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -3900,6 +3900,48 @@ 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 always-on-clocks; */ >> + if (clksize == 0) { >> + if (of_property_read_bool(np, "always-on-clocks")) >> + core->flags |= CLK_IS_CRITICAL; > > Why must we set the CLK_IS_CRITICAL flag like this? I don't quite understand the question here. Clock which shouldn't be turned off should have CLK_IS_CRITICAL flag set. > Instead, when the > clk provider is registered, parse the node of the provider and get the > clks to call clk_prepare_enable() on. We can set the critical flag or > make a new flag that causes clk_disable_unprepare() to not actually turn > the clk off, if we have some sort of underflow issue with other > consumers. Does that fail somehow? Would your proposal be something that would have to be implemented in every single clock driver separately ? >> + return; >> + } >> + >> + if (!core->ops->match_clkspec) >> + return; >> + >> + clkspec.np = np; >> + clktotal = of_property_count_u32_elems(np, "always-on-clocks"); >> + clktotal /= clksize; >> + for (index = 0; index < clktotal; index++) { >> + for (i = 0; i < clksize; i++) { > > I'm mainly thinking that we're going to spin on this loop constantly for > any clk providers that have many clks to register, but only a few to > keep always on. It would be best to avoid that and only run through the > DT property once. Where could this be implemented in the clock core ? >> + ret = of_property_read_u32_index(np, "always-on-clocks", >> + (index * clksize) + i, >> + &(clkspec.args[i])); >> + if (ret) { >> + pr_warn("Skipping always-on-clocks index %d (ret=%d)\n", >> + i, ret); >> + } >> + } >> + if (!core->ops->match_clkspec(hw, &clkspec)) > > This callback is provider specific, and not necessarily clk_hw specific. > For example, the clk_ops could be for a generic gate bit, but the > provider wants to keep that gate always on. To implement such a clk we > would have to copy the generic gate clk_ops and set this match_clkspec > op. I'd like to avoid that if possible. If the clk_op must exist, then > perhaps it should be in clk_init_data, which is sort of the place where > we put provider specific information for a clk, i.e. clk_parent_data. The core->ops is copied from struct clk_init_data .ops in __clk_register() , just before __clk_register_critical_clock() is called, so that op is already in clk_init_data.
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index b70769d0db99f..6b07f1a086277 100644 --- a/drivers/clk/clk.c +++ b/drivers/clk/clk.c @@ -3900,6 +3900,48 @@ 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 always-on-clocks; */ + if (clksize == 0) { + if (of_property_read_bool(np, "always-on-clocks")) + core->flags |= CLK_IS_CRITICAL; + return; + } + + if (!core->ops->match_clkspec) + return; + + clkspec.np = np; + clktotal = of_property_count_u32_elems(np, "always-on-clocks"); + clktotal /= clksize; + for (index = 0; index < clktotal; index++) { + for (i = 0; i < clksize; i++) { + ret = of_property_read_u32_index(np, "always-on-clocks", + (index * clksize) + i, + &(clkspec.args[i])); + if (ret) { + pr_warn("Skipping always-on-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) { @@ -3944,6 +3986,8 @@ __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 dec1bcae43790..e02a66dc482be 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 "always-on-clocks" property of a clock controller allows listing clock which must never be turned off. Clock listed in the "always-on-clocks" property may have other consumers in DT, listing the clock in "always-on-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 "always-on-clocks" instead. Unlike "assigned-clocks", the "always-on-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 "always-on-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 V4: - Rename DT property critical-clocks to always-on-clocks --- drivers/clk/clk.c | 44 ++++++++++++++++++++++++++++++++++++ include/linux/clk-provider.h | 3 +++ 2 files changed, 47 insertions(+)