[PATCH v7 4/5] clk: Provide critical clock support

Lee Jones
2015-07-22T13:16:52Z

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 critical clocks to be supplied
which must be kept ungated. Each clock mentioned in the newly
introduced 'critical-clock' property 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 normal
clk_disable_unused() and disable_clock() procedures.

Note that it will still be possible for knowledgeable drivers to turn
these clocks off using clk_{enable,disable}_critical() calls.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
drivers/clk/clk-conf.c | 45 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 44 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
index aad4796..f83c1c2 100644
--- a/drivers/clk/clk-conf.c
+++ b/drivers/clk/clk-conf.c
@@ -116,6 +116,45 @@ static int __set_clk_rates(struct device_node *node, bool clk_supplier)
return 0;
}

+static int __set_critical_clocks(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, "critical-clock", prop, cur, index) {
+ clkspec.np = node;
+ clkspec.args_count = 1;
+ clkspec.args[0] = index;
+
+ clk = of_clk_get_from_provider(&clkspec);
+ if (IS_ERR(clk)) {
+ pr_err("clk: couldn't get clock %u for %s\n",
+ index, node->full_name);
+ return PTR_ERR(clk);
+ }
+
+ clk_init_critical(clk);
+
+ ret = clk_prepare_enable(clk);
+ if (ret) {
+ pr_err("Failed to enable clock %u for %s: %d\n",
+ index, node->full_name, ret);
+ return ret;
+ }
+
+ pr_debug("Setting clock as critical %pC\n", clk);
+ }
+
+ return 0;
+}
+
/**
* of_clk_set_defaults() - parse and set assigned clocks configuration
* @node: device node to apply clock settings for
@@ -139,6 +178,10 @@ 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_critical_clocks(node, clk_supplier);
}
EXPORT_SYMBOL_GPL(of_clk_set_defaults);
--
1.9.1