When automatic clock gating is enabled, runtime PM (RPM) isn't entered
even if enabled for a CMU if a sysreg clock exists and is provided by
this CMU (as is generally the case).

The reason is that this driver acquires a CMU's sysreg registers using
syscon_regmap_lookup_by_phandle() which ends up preparing the sysreg
clock. Given the sysreg clock is provided by this CMU, this CMU's usage
count is therefore bumped and RPM can not be entered as this CMU never
becomes idle.

Switch to using device_node_to_regmap() which doesn't handle resources
(the clock), leaving the CMU's usage count unaffected.

Note1: sysreg clock handling is completely removed with this commit
because sysreg register access is only required during suspend/resume.
In the runtime suspend case, we would have to enable the clock to read
the registers, but we can not do that as that would cause a resume of
this driver which is not allowed. This is not a problem because we
would only need to handle the clock manually if automatic clock gating
wasn't enabled in the first. This code is only relevant if automatic
clock gating is enabled, though.

Fixes: 298fac4f4b96 ("clk: samsung: Implement automatic clock gating mode for CMUs")
Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
 drivers/clk/samsung/clk.c | 92 +++++++++++++++++++++++++++++++++++------------
 drivers/clk/samsung/clk.h |  2 ++
 2 files changed, 71 insertions(+), 23 deletions(-)

diff --git a/drivers/clk/samsung/clk.c b/drivers/clk/samsung/clk.c
index 9f68f079fd552f8dfb6898dbfb47dec0e84c626c..6515df81fcbc79b90f5262843e67575f6a4e0dda 100644
--- a/drivers/clk/samsung/clk.c
+++ b/drivers/clk/samsung/clk.c
@@ -9,11 +9,13 @@
  */
 
 #include <linux/slab.h>
+#include <linux/clk.h>
 #include <linux/clkdev.h>
 #include <linux/clk-provider.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
 #include <linux/mod_devicetable.h>
+#include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/regmap.h>
 #include <linux/syscore_ops.h>
@@ -489,6 +491,50 @@ void __init samsung_cmu_register_clocks(struct samsung_clk_provider *ctx,
 		samsung_clk_register_cpu(ctx, cmu->cpu_clks, cmu->nr_cpu_clks);
 }
 
+static int samsung_get_sysreg_regmap(struct device_node *np,
+				     struct samsung_clk_provider *ctx)
+{
+	struct device_node *sysreg_np;
+	struct clk *sysreg_clk;
+	struct regmap *regmap;
+	int ret;
+
+	sysreg_np = of_parse_phandle(np, "samsung,sysreg", 0);
+	if (!sysreg_np)
+		return -ENODEV;
+
+	sysreg_clk = of_clk_get(sysreg_np, 0);
+	if (IS_ERR(sysreg_clk)) {
+		ret = PTR_ERR(sysreg_clk);
+		/* clock is optional */
+		if (ret != -ENOENT) {
+			pr_warn("%pOF: Unable to get sysreg clock: %d\n", np,
+				ret);
+			goto put_sysreg_np;
+		}
+		sysreg_clk = NULL;
+	}
+
+	regmap = device_node_to_regmap(sysreg_np);
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		pr_warn("%pOF: Unable to get CMU sysreg: %d\n", np, ret);
+		goto put_clk;
+	}
+
+	ctx->sysreg_clk = sysreg_clk;
+	ctx->sysreg = regmap;
+
+	of_node_put(sysreg_np);
+	return 0;
+
+put_clk:
+	clk_put(sysreg_clk);
+put_sysreg_np:
+	of_node_put(sysreg_np);
+	return ret;
+}
+
 /* Each bit enable/disables DRCG of a bus component */
 #define DRCG_EN_MSK	GENMASK(31, 0)
 #define MEMCLK_EN	BIT(0)
@@ -499,32 +545,32 @@ void samsung_en_dyn_root_clk_gating(struct device_node *np,
 				    const struct samsung_cmu_info *cmu,
 				    bool cmu_has_pm)
 {
+	int ret;
+
 	if (!ctx->auto_clock_gate)
 		return;
 
-	ctx->sysreg = syscon_regmap_lookup_by_phandle(np, "samsung,sysreg");
-	if (IS_ERR(ctx->sysreg)) {
-		pr_warn("%pOF: Unable to get CMU sysreg\n", np);
-		ctx->sysreg = NULL;
-	} else {
-		/* Enable DRCG for all bus components */
-		regmap_write(ctx->sysreg, ctx->drcg_offset, DRCG_EN_MSK);
-		/* Enable memclk gate (not present on all sysreg) */
-		if (ctx->memclk_offset)
-			regmap_write_bits(ctx->sysreg, ctx->memclk_offset,
-					  MEMCLK_EN, 0x0);
-
-		if (!cmu_has_pm)
-			/*
-			 * When a CMU has PM support, clocks are saved/restored
-			 * via its PM handlers, so only register them with the
-			 * syscore suspend / resume paths if PM is not in use.
-			 */
-			samsung_clk_extended_sleep_init(NULL, ctx->sysreg,
-							cmu->sysreg_clk_regs,
-							cmu->nr_sysreg_clk_regs,
-							NULL, 0);
-	}
+	ret = samsung_get_sysreg_regmap(np, ctx);
+	if (ret)
+		return;
+
+	/* Enable DRCG for all bus components */
+	regmap_write(ctx->sysreg, ctx->drcg_offset, DRCG_EN_MSK);
+	/* Enable memclk gate (not present on all sysreg) */
+	if (ctx->memclk_offset)
+		regmap_write_bits(ctx->sysreg, ctx->memclk_offset,
+				  MEMCLK_EN, 0x0);
+
+	if (!cmu_has_pm)
+		/*
+		 * When a CMU has PM support, clocks are saved/restored via its
+		 * PM handlers, so only register them with the syscore
+		 * suspend / resume paths if PM is not in use.
+		 */
+		samsung_clk_extended_sleep_init(NULL, ctx->sysreg,
+						cmu->sysreg_clk_regs,
+						cmu->nr_sysreg_clk_regs,
+						NULL, 0);
 }
 
 /*
diff --git a/drivers/clk/samsung/clk.h b/drivers/clk/samsung/clk.h
index b1192ca03db5035cc485771ff5597cf132234a2a..deb426fbb0942f21b63c583f0ad55738239b04e4 100644
--- a/drivers/clk/samsung/clk.h
+++ b/drivers/clk/samsung/clk.h
@@ -21,6 +21,7 @@
  * @reg_base: virtual address for the register base
  * @dev: clock provider device needed for runtime PM
  * @sysreg: syscon regmap for clock-provider sysreg controller
+ * @sysreg_clk: clock for sysreg access, if required
  * @lock: maintains exclusion between callbacks for a given clock-provider
  * @auto_clock_gate: enable auto clk mode for all clocks in clock-provider
  * @gate_dbg_offset: gate debug reg offset. Used for all gates in auto clk mode
@@ -33,6 +34,7 @@ struct samsung_clk_provider {
 	void __iomem *reg_base;
 	struct device *dev;
 	struct regmap *sysreg;
+	struct clk *sysreg_clk;
 	spinlock_t lock;
 	bool auto_clock_gate;
 	u32 gate_dbg_offset;

-- 
2.52.0.457.g6b5491de43-goog

On 09/01/2026 18:27, André Draszik wrote:
> When automatic clock gating is enabled, runtime PM (RPM) isn't entered
> even if enabled for a CMU if a sysreg clock exists and is provided by
> this CMU (as is generally the case).
> 
> The reason is that this driver acquires a CMU's sysreg registers using
> syscon_regmap_lookup_by_phandle() which ends up preparing the sysreg
> clock. Given the sysreg clock is provided by this CMU, this CMU's usage
> count is therefore bumped and RPM can not be entered as this CMU never
> becomes idle.
> 
> Switch to using device_node_to_regmap() which doesn't handle resources
> (the clock), leaving the CMU's usage count unaffected.
> 
> Note1: sysreg clock handling is completely removed with this commit

I miss where do you remove in this commit the sysreg clock handling?

> because sysreg register access is only required during suspend/resume.
> In the runtime suspend case, we would have to enable the clock to read
> the registers, but we can not do that as that would cause a resume of
> this driver which is not allowed. This is not a problem because we
> would only need to handle the clock manually if automatic clock gating
> wasn't enabled in the first. This code is only relevant if automatic
> clock gating is enabled, though.
> 
> Fixes: 298fac4f4b96 ("clk: samsung: Implement automatic clock gating mode for CMUs")
> Signed-off-by: André Draszik <andre.draszik@linaro.org>
> ---
>  drivers/clk/samsung/clk.c | 92 +++++++++++++++++++++++++++++++++++------------
>  drivers/clk/samsung/clk.h |  2 ++
>  2 files changed, 71 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/clk/samsung/clk.c b/drivers/clk/samsung/clk.c
> index 9f68f079fd552f8dfb6898dbfb47dec0e84c626c..6515df81fcbc79b90f5262843e67575f6a4e0dda 100644
> --- a/drivers/clk/samsung/clk.c
> +++ b/drivers/clk/samsung/clk.c
> @@ -9,11 +9,13 @@
>   */
>  
>  #include <linux/slab.h>
> +#include <linux/clk.h>
>  #include <linux/clkdev.h>
>  #include <linux/clk-provider.h>
>  #include <linux/io.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/mod_devicetable.h>
> +#include <linux/of.h>
>  #include <linux/of_address.h>
>  #include <linux/regmap.h>
>  #include <linux/syscore_ops.h>
> @@ -489,6 +491,50 @@ void __init samsung_cmu_register_clocks(struct samsung_clk_provider *ctx,
>  		samsung_clk_register_cpu(ctx, cmu->cpu_clks, cmu->nr_cpu_clks);
>  }
>  
> +static int samsung_get_sysreg_regmap(struct device_node *np,
> +				     struct samsung_clk_provider *ctx)
> +{
> +	struct device_node *sysreg_np;
> +	struct clk *sysreg_clk;
> +	struct regmap *regmap;
> +	int ret;
> +
> +	sysreg_np = of_parse_phandle(np, "samsung,sysreg", 0);
> +	if (!sysreg_np)
> +		return -ENODEV;
> +
> +	sysreg_clk = of_clk_get(sysreg_np, 0);

I don't think you should be poking clock of some other device. This
clearly breaks encapsulation. What sysreg is needs to do to access
registers, is only business of sysreg. No other drivers should
re-implement this.

> +	if (IS_ERR(sysreg_clk)) {
> +		ret = PTR_ERR(sysreg_clk);
> +		/* clock is optional */
> +		if (ret != -ENOENT) {
> +			pr_warn("%pOF: Unable to get sysreg clock: %d\n", np,
> +				ret);
> +			goto put_sysreg_np;
> +		}
> +		sysreg_clk = NULL;
> +	}


Best regards,
Krzysztof

Hi Krzysztof,

On Sat, 2026-01-17 at 20:25 +0100, Krzysztof Kozlowski wrote:
> On 09/01/2026 18:27, André Draszik wrote:
> > When automatic clock gating is enabled, runtime PM (RPM) isn't entered
> > even if enabled for a CMU if a sysreg clock exists and is provided by
> > this CMU (as is generally the case).
> > 
> > The reason is that this driver acquires a CMU's sysreg registers using
> > syscon_regmap_lookup_by_phandle() which ends up preparing the sysreg
> > clock. Given the sysreg clock is provided by this CMU, this CMU's usage
> > count is therefore bumped and RPM can not be entered as this CMU never
> > becomes idle.
> > 
> > Switch to using device_node_to_regmap() which doesn't handle resources
> > (the clock), leaving the CMU's usage count unaffected.
> > 
> > Note1: sysreg clock handling is completely removed with this commit
> 
> I miss where do you remove in this commit the sysreg clock handling?

The CMU driver originally used syscon_regmap_lookup_by_phandle() for sysreg,
which does clk_get() and clk_prepare(), and then implicitly and for each
register access clk_enable()/disable() for the clock specified in DT for the
(sysreg) node.

This commit changes it to using device_node_to_regmap(), which does nothing
with the clock (or any other resources). I opted to have the CMU driver still
do a clk_get(), so that the relationship is still visible, e.g. in
$debugfs/clk/clk_summary.

> > because sysreg register access is only required during suspend/resume.
> > In the runtime suspend case, we would have to enable the clock to read
> > the registers, but we can not do that as that would cause a resume of
> > this driver which is not allowed. This is not a problem because we
> > would only need to handle the clock manually if automatic clock gating
> > wasn't enabled in the first. This code is only relevant if automatic
> > clock gating is enabled, though.
> > 
> > Fixes: 298fac4f4b96 ("clk: samsung: Implement automatic clock gating mode for CMUs")
> > Signed-off-by: André Draszik <andre.draszik@linaro.org>
> > ---
> >  drivers/clk/samsung/clk.c | 92 +++++++++++++++++++++++++++++++++++------------
> >  drivers/clk/samsung/clk.h |  2 ++
> >  2 files changed, 71 insertions(+), 23 deletions(-)
> > 
> > diff --git a/drivers/clk/samsung/clk.c b/drivers/clk/samsung/clk.c
> > index 9f68f079fd552f8dfb6898dbfb47dec0e84c626c..6515df81fcbc79b90f5262843e67575f6a4e0dda 100644
> > --- a/drivers/clk/samsung/clk.c
> > +++ b/drivers/clk/samsung/clk.c
> > @@ -9,11 +9,13 @@
> >   */
> >  
> >  #include <linux/slab.h>
> > +#include <linux/clk.h>
> >  #include <linux/clkdev.h>
> >  #include <linux/clk-provider.h>
> >  #include <linux/io.h>
> >  #include <linux/mfd/syscon.h>
> >  #include <linux/mod_devicetable.h>
> > +#include <linux/of.h>
> >  #include <linux/of_address.h>
> >  #include <linux/regmap.h>
> >  #include <linux/syscore_ops.h>
> > @@ -489,6 +491,50 @@ void __init samsung_cmu_register_clocks(struct samsung_clk_provider *ctx,
> >  		samsung_clk_register_cpu(ctx, cmu->cpu_clks, cmu->nr_cpu_clks);
> >  }
> >  
> > +static int samsung_get_sysreg_regmap(struct device_node *np,
> > +				     struct samsung_clk_provider *ctx)
> > +{
> > +	struct device_node *sysreg_np;
> > +	struct clk *sysreg_clk;
> > +	struct regmap *regmap;
> > +	int ret;
> > +
> > +	sysreg_np = of_parse_phandle(np, "samsung,sysreg", 0);
> > +	if (!sysreg_np)
> > +		return -ENODEV;
> > +
> > +	sysreg_clk = of_clk_get(sysreg_np, 0);
> 
> I don't think you should be poking clock of some other device. This
> clearly breaks encapsulation. What sysreg is needs to do to access
> registers, is only business of sysreg. No other drivers should
> re-implement this.

Similarly, to how other drivers (like UFS and peric/USI) also poke in
the sysreg region in a similar way, the CMU related parts of sysreg are
handled in this driver, though, as only the CMU driver knows how to
configure them based on the gating (auto vs. manual).

No separate driver was sysreg was added when this code was introduced.
The clk_get() used to be part of syscon_regmap_lookup_by_phandle(), and
I chose to keep only that, as per above.

I propose to add an actual sysreg driver once the need arises, then
this can also move, but for now keeping it here seems straight forward.

Is that OK with you?

Cheers,
Andre'

On Mon, 2026-01-19 at 15:00 +0000, André Draszik wrote:
> Hi Krzysztof,
> 
> On Sat, 2026-01-17 at 20:25 +0100, Krzysztof Kozlowski wrote:
> > On 09/01/2026 18:27, André Draszik wrote:
> > > When automatic clock gating is enabled, runtime PM (RPM) isn't entered
> > > even if enabled for a CMU if a sysreg clock exists and is provided by
> > > this CMU (as is generally the case).
> > > 
> > > The reason is that this driver acquires a CMU's sysreg registers using
> > > syscon_regmap_lookup_by_phandle() which ends up preparing the sysreg
> > > clock. Given the sysreg clock is provided by this CMU, this CMU's usage
> > > count is therefore bumped and RPM can not be entered as this CMU never
> > > becomes idle.
> > > 
> > > Switch to using device_node_to_regmap() which doesn't handle resources
> > > (the clock), leaving the CMU's usage count unaffected.
> > > 
> > > Note1: sysreg clock handling is completely removed with this commit
> > 
> > I miss where do you remove in this commit the sysreg clock handling?
> 
> The CMU driver originally used syscon_regmap_lookup_by_phandle() for sysreg,
> which does clk_get() and clk_prepare(), and then implicitly and for each
> register access clk_enable()/disable() for the clock specified in DT for the
> (sysreg) node.
> 
> This commit changes it to using device_node_to_regmap(), which does nothing
> with the clock (or any other resources). I opted to have the CMU driver still
> do a clk_get(), so that the relationship is still visible, e.g. in
> $debugfs/clk/clk_summary.
> 
> > > because sysreg register access is only required during suspend/resume.
> > > In the runtime suspend case, we would have to enable the clock to read
> > > the registers, but we can not do that as that would cause a resume of
> > > this driver which is not allowed. This is not a problem because we
> > > would only need to handle the clock manually if automatic clock gating
> > > wasn't enabled in the first. This code is only relevant if automatic
> > > clock gating is enabled, though.
> > > 
> > > Fixes: 298fac4f4b96 ("clk: samsung: Implement automatic clock gating mode for CMUs")
> > > Signed-off-by: André Draszik <andre.draszik@linaro.org>
> > > ---
> > >  drivers/clk/samsung/clk.c | 92 +++++++++++++++++++++++++++++++++++------------
> > >  drivers/clk/samsung/clk.h |  2 ++
> > >  2 files changed, 71 insertions(+), 23 deletions(-)
> > > 
> > > diff --git a/drivers/clk/samsung/clk.c b/drivers/clk/samsung/clk.c
> > > index 9f68f079fd552f8dfb6898dbfb47dec0e84c626c..6515df81fcbc79b90f5262843e67575f6a4e0dda 100644
> > > --- a/drivers/clk/samsung/clk.c
> > > +++ b/drivers/clk/samsung/clk.c
> > > @@ -9,11 +9,13 @@
> > >   */
> > >  
> > >  #include <linux/slab.h>
> > > +#include <linux/clk.h>
> > >  #include <linux/clkdev.h>
> > >  #include <linux/clk-provider.h>
> > >  #include <linux/io.h>
> > >  #include <linux/mfd/syscon.h>
> > >  #include <linux/mod_devicetable.h>
> > > +#include <linux/of.h>
> > >  #include <linux/of_address.h>
> > >  #include <linux/regmap.h>
> > >  #include <linux/syscore_ops.h>
> > > @@ -489,6 +491,50 @@ void __init samsung_cmu_register_clocks(struct samsung_clk_provider *ctx,
> > >  		samsung_clk_register_cpu(ctx, cmu->cpu_clks, cmu->nr_cpu_clks);
> > >  }
> > >  
> > > +static int samsung_get_sysreg_regmap(struct device_node *np,
> > > +				     struct samsung_clk_provider *ctx)
> > > +{
> > > +	struct device_node *sysreg_np;
> > > +	struct clk *sysreg_clk;
> > > +	struct regmap *regmap;
> > > +	int ret;
> > > +
> > > +	sysreg_np = of_parse_phandle(np, "samsung,sysreg", 0);
> > > +	if (!sysreg_np)
> > > +		return -ENODEV;
> > > +
> > > +	sysreg_clk = of_clk_get(sysreg_np, 0);
> > 
> > I don't think you should be poking clock of some other device. This
> > clearly breaks encapsulation. What sysreg is needs to do to access
> > registers, is only business of sysreg. No other drivers should
> > re-implement this.
> 
> Similarly, to how other drivers (like UFS and peric/USI) also poke in
> the sysreg region in a similar way, the CMU related parts of sysreg are
> handled in this driver, though, as only the CMU driver knows how to
> configure them based on the gating (auto vs. manual).
> 
> No separate driver was sysreg was added when this code was introduced.
> The clk_get() used to be part of syscon_regmap_lookup_by_phandle(), and
> I chose to keep only that, as per above.
> 
> I propose to add an actual sysreg driver once the need arises, then
> this can also move, but for now keeping it here seems straight forward.
> 
> Is that OK with you?

Forgot to say, I can of course remove all clock related code (clk_get() etc).

What do you think? Is that acceptable?


CHeers,
Andre'