linux-kernel - [RFC PATCH 1/2] clk: add support for critical always-on clocks

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Date:   Tue, 13 Sep 2022 12:21:40 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        abelvesa@...nel.org, abel.vesa@...aro.org, mturquette@...libre.com,
        sboyd@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com
Cc:     linux-kernel@...r.kernel.org, Peng Fan <peng.fan@....com>,
        linux-imx@....com, linux-arm-kernel@...ts.infradead.org,
        linux-clk@...r.kernel.org
Subject: [RFC PATCH 1/2] clk: add support for critical always-on clocks

Add support to mark specific clocks as always-on (critical), like the
regulator-alawys-on property. So the platform integrators can specify
the property on a per device basis by specifying it within the firmware
and not only within the driver. Unlike the regulator framework the clock
framework uses a 1:n matching, which means 1 firmware node can provide
up to n clock providers. Therefore the binding uses a string-array so we
can specify n clock providers as critical.

Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
---
 drivers/clk/clk.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 7fc191c15507..c3651bf96f90 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3825,6 +3825,22 @@ static int clk_cpy_name(const char **dst_p, const char *src, bool must_exist)
 	return 0;
 }
 
+static void clk_core_check_critical(struct clk_core *core)
+{
+	struct fwnode_handle *fwnode = of_fwnode_handle(core->of_node);
+	const char *prop = "clocks-always-on";
+	int ret;
+
+	/* Very early added clocks don't have a fwnode */
+	if (!fwnode || !fwnode_property_present(fwnode, prop))
+		return;
+
+	/* Mark clock as critical if listed within the clocks-always-on array */
+	ret = fwnode_property_match_string(fwnode, prop, core->name);
+	if (!ret)
+		core->flags |= CLK_IS_CRITICAL;
+}
+
 static int clk_core_populate_parent_map(struct clk_core *core,
 					const struct clk_init_data *init)
 {
@@ -3946,6 +3962,8 @@ __clk_register(struct device *dev, struct device_node *np, struct clk_hw *hw)
 	core->min_rate = 0;
 	core->max_rate = ULONG_MAX;
 
+	clk_core_check_critical(core);
+
 	ret = clk_core_populate_parent_map(core, init);
 	if (ret)
 		goto fail_parents;
-- 
2.30.2