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Subject[PATCH v5 3/4] clk: Provide always-on clock support
Date
Lots of platforms contain clocks which if turned off would prove fatal.
The only way to recover from these catastrophic failures is to restart
the board(s). Now, when a clock provider is registered with the
framework it is possible for a list of always-on clocks to be supplied
which must be kept ungated. Each clock mentioned in the newly
introduced 'clock-always-on' will be clk_prepare_enable()d where the
normal references will be taken. This will prevent the common clk
framework from attempting to gate them during the clk_disable_unused()
and disable_clock() procedures.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/clk/clk-conf.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
index aad4796..22b8fdd 100644
--- a/drivers/clk/clk-conf.c
+++ b/drivers/clk/clk-conf.c
@@ -116,6 +116,43 @@ static int __set_clk_rates(struct device_node *node, bool clk_supplier)
return 0;
}

+static int __set_clk_always_on(struct device_node *node, bool clk_supplier)
+{
+ struct of_phandle_args clkspec;
+ struct clk *clk;
+ struct property *prop;
+ const __be32 *cur;
+ uint32_t index;
+ int ret;
+
+ if (!clk_supplier)
+ return 0;
+
+ of_property_for_each_u32(node, "clock-always-on", prop, cur, index) {
+ clkspec.np = node;
+ clkspec.args_count = 1;
+ clkspec.args[0] = index;
+
+ clk = of_clk_get_by_clkspec(&clkspec);
+ if (IS_ERR(clk)) {
+ pr_err("clk: couldn't get clock %d for %s\n",
+ index, node->full_name);
+ return PTR_ERR(clk);
+ }
+
+ ret = clk_prepare_enable(clk);
+ if (ret) {
+ pr_err("Failed to enable clock %d for %s: %d\n",
+ index, node->full_name, ret);
+ return ret;
+ }
+
+ pr_debug("Set clock %s as always-on\n", __clk_get_name(clk));
+ }
+
+ return 0;
+}
+
/**
* of_clk_set_defaults() - parse and set assigned clocks configuration
* @node: device node to apply clock settings for
@@ -139,6 +176,10 @@ int of_clk_set_defaults(struct device_node *node, bool clk_supplier)
if (rc < 0)
return rc;

- return __set_clk_rates(node, clk_supplier);
+ rc = __set_clk_rates(node, clk_supplier);
+ if (rc < 0)
+ return rc;
+
+ return __set_clk_always_on(node, clk_supplier);
}
EXPORT_SYMBOL_GPL(of_clk_set_defaults);
--
1.9.1


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