[PATCH 01/13] clk: add new flag CLK_ROUNDING_FW_MANAGED

From: Brian Masney <bmasney@redhat.com>
Date: 2026-02-26 18:17:45
Also in: arm-scmi, imx, linux-arm-msm, linux-clk, linux-renesas-soc, linux-samsung-soc, lkml
Subsystem: common clk framework, the rest · Maintainers: Michael Turquette, Stephen Boyd, Linus Torvalds

There are some clocks where the rounding is managed by the hardware, and
the determine_rate() clk ops is just a noop that simply returns 0. Add a
new flag for these type of clocks, and update the clk core so that the
determine_rate() clk op is not required when this flag is set.

Signed-off-by: Brian Masney <bmasney@redhat.com>

---
To: Michael Turquette <mturquette@baylibre.com>
To: Stephen Boyd <sboyd@kernel.org>
To: Abel Vesa <abelvesa@kernel.org>
To: Andrea della Porta <andrea.porta@suse.com>
To: Baolin Wang <baolin.wang@linux.alibaba.com>
To: Bjorn Andersson <andersson@kernel.org>
To: Chanwoo Choi <cw00.choi@samsung.com>
To: Frank Li <Frank.Li@nxp.com>
To: Geert Uytterhoeven <geert+renesas@glider.be>
To: Krzysztof Kozlowski <krzk@kernel.org>
To: Orson Zhai <orsonzhai@gmail.com>
To: Sascha Hauer <s.hauer@pengutronix.de>
To: Sudeep Holla <sudeep.holla@kernel.org>
To: Sylwester Nawrocki <s.nawrocki@samsung.com>
To: Tudor Ambarus <tudor.ambarus@linaro.org>
Cc: linux-clk@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: arm-scmi@vger.kernel.org
Cc: Chunyan Zhang <zhang.lyra@gmail.com>
Cc: Cristian Marussi <cristian.marussi@arm.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: imx@lists.linux.dev
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-arm-msm@vger.kernel.org
Cc: linux-renesas-soc@vger.kernel.org
Cc: linux-samsung-soc@vger.kernel.org
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
---
 drivers/clk/clk.c            | 24 +++++++++++++++++++++---
 include/linux/clk-provider.h |  2 ++
 2 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index fd418dc988b1c60c49e3ac9c0c44aa132dd5da28..0a522a0817411c7f7c6e9cffd6f024e672a331a8 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c

@@ -1557,6 +1557,20 @@ static int __init clk_disable_unused(void)
 }
 late_initcall_sync(clk_disable_unused);
 
+/**
+ * clk_is_rounding_fw_managed - Check to see if clk rounding is handled by the
+ * firmware.
+ * @core: the clk to check
+ *
+ * Clks that have this flag enabled do not need to have a determine_rate() op
+ * set, and will always return success for any rounding operation since the
+ * firmware will deal with the rounding.
+ */
+static inline bool clk_is_rounding_fw_managed(struct clk_core *core)
+{
+	return core->flags & CLK_ROUNDING_FW_MANAGED;
+}
+
 static int clk_core_determine_round_nolock(struct clk_core *core,
 					   struct clk_rate_request *req)
 {

@@ -1589,6 +1603,8 @@ static int clk_core_determine_round_nolock(struct clk_core *core,
 		req->rate = core->rate;
 	} else if (core->ops->determine_rate) {
 		return core->ops->determine_rate(core->hw, req);
+	} else if (clk_is_rounding_fw_managed(core)) {
+		return 0;
 	} else {
 		return -EINVAL;
 	}

@@ -1673,7 +1689,7 @@ EXPORT_SYMBOL_GPL(clk_hw_forward_rate_request);
 
 static bool clk_core_can_round(struct clk_core * const core)
 {
-	return core->ops->determine_rate;
+	return core->ops->determine_rate || clk_is_rounding_fw_managed(core);
 }
 
 static int clk_core_round_rate_nolock(struct clk_core *core,

@@ -3528,6 +3544,7 @@ static const struct {
 	ENTRY(CLK_IS_CRITICAL),
 	ENTRY(CLK_OPS_PARENT_ENABLE),
 	ENTRY(CLK_DUTY_CYCLE_PARENT),
+	ENTRY(CLK_ROUNDING_FW_MANAGED),
 #undef ENTRY
 };

@@ -3906,7 +3923,7 @@ static int __clk_core_init(struct clk_core *core)
 
 	/* check that clk_ops are sane.  See Documentation/driver-api/clk.rst */
 	if (core->ops->set_rate && !core->ops->determine_rate &&
-	      core->ops->recalc_rate) {
+	      core->ops->recalc_rate && !clk_is_rounding_fw_managed(core)) {
 		pr_err("%s: %s must implement .determine_rate in addition to .recalc_rate\n",
 		       __func__, core->name);
 		ret = -EINVAL;

@@ -3920,7 +3937,8 @@ static int __clk_core_init(struct clk_core *core)
 		goto out;
 	}
 
-	if (core->ops->set_parent && !core->ops->determine_rate) {
+	if (core->ops->set_parent && !core->ops->determine_rate &&
+	    !clk_is_rounding_fw_managed(core)) {
 		pr_err("%s: %s must implement .set_parent & .determine_rate\n",
 			__func__, core->name);
 		ret = -EINVAL;

diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 1cda2c78dffaff037f0f16b0f11106b63b3a746f..187f8248a9c840c701cbbba99bb7cdeef7b654ee 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h

@@ -32,6 +32,8 @@
 #define CLK_OPS_PARENT_ENABLE	BIT(12)
 /* duty cycle call may be forwarded to the parent clock */
 #define CLK_DUTY_CYCLE_PARENT	BIT(13)
+/* clock rate rounding is managed by firmware, don't require determine_rate */
+#define CLK_ROUNDING_FW_MANAGED		BIT(14)
 
 struct clk;
 struct clk_hw;

-- 
2.53.0

`h`	back out one level
`j`	next message in thread
`k`	previous message in thread
`l`	drill in
`Esc`	close help / fold thread tree
`?`	toggle this help