Re: [PATCH V3 2/2] clk: scmi: support state_ctrl_forbidden

[Cristian Marussi <cristian.marussi@arm.com>]

On Mon, Jan 15, 2024 at 02:02:03PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@nxp.com>
> 
> Some clocks may exported to linux, while those clocks are not allowed
> to configure by Linux. For example:
> 
> SYS_CLK1-----
>              \
> 	     --MUX--->MMC1_CLK
>              /
> SYS_CLK2-----
> 
> MMC1 needs set parent, so SYS_CLK1 and SYS_CLK2 are exported to Linux,
> then the clk propagation will touch SYS_CLK1 or SYS_CLK2.
> So we need bypass the failure for SYS_CLK1 or SYS_CLK2 when enable
> the clock of MMC1.
> 

Hi,

so this looks good to me and apparently (as noted) the CLK framework is OK
with a driver swallowing the -EACCESS when a clock is immutable, BUT at the
end of the day do we even need to try this SCMI call and hide the failure in
case of immutable clocks ?

I mean, what if we just dont provide any callback for enable/disable...I can
see plenty of drivers not providing those callbacks ?
Maybe this is probably more of a question for Stephen...

IOW what about doing something like below...does it make any difference
in your setup ? works fine in my emulated env

(Note that last snippet in clk_gate_restore_context() is probably a fix
 that needs to be added anyway by looking at the code in clk.c)

Thanks,
Cristian

--->8----
diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
index 5327e0547741..a669a2f2f78b 100644
--- a/drivers/clk/clk-scmi.c
+++ b/drivers/clk/clk-scmi.c
@@ -121,11 +121,7 @@ static int scmi_clk_enable(struct clk_hw *hw)
 	struct scmi_clk *clk = to_scmi_clk(hw);
 	int ret;
 
-	ret = scmi_proto_clk_ops->enable(clk->ph, clk->id, NOT_ATOMIC);
-	if (ret == -EACCES && clk->info->state_ctrl_forbidden)
-		return 0;
-
-	return ret;
+	return scmi_proto_clk_ops->enable(clk->ph, clk->id, NOT_ATOMIC);
 }
 
 static void scmi_clk_disable(struct clk_hw *hw)
@@ -140,11 +136,7 @@ static int scmi_clk_atomic_enable(struct clk_hw *hw)
 	struct scmi_clk *clk = to_scmi_clk(hw);
 	int ret;
 
-	ret = scmi_proto_clk_ops->enable(clk->ph, clk->id, ATOMIC);
-	if (ret == -EACCES && clk->info->state_ctrl_forbidden)
-		return 0;
-
-	return ret;
+	return scmi_proto_clk_ops->enable(clk->ph, clk->id, ATOMIC);
 }
 
 static void scmi_clk_atomic_disable(struct clk_hw *hw)
@@ -204,6 +196,15 @@ static const struct clk_ops scmi_atomic_clk_ops = {
 	.determine_rate = scmi_clk_determine_rate,
 };
 
+static const struct clk_ops scmi_no_state_ctrl_clk_ops = {
+	.recalc_rate = scmi_clk_recalc_rate,
+	.round_rate = scmi_clk_round_rate,
+	.set_rate = scmi_clk_set_rate,
+	.set_parent = scmi_clk_set_parent,
+	.get_parent = scmi_clk_get_parent,
+	.determine_rate = scmi_clk_determine_rate,
+};
+
 static int scmi_clk_ops_init(struct device *dev, struct scmi_clk *sclk,
 			     const struct clk_ops *scmi_ops)
 {
@@ -300,8 +301,10 @@ static int scmi_clocks_probe(struct scmi_device *sdev)
 		 * specify (or support) an enable_latency associated with a
 		 * clock, we default to use atomic operations mode.
 		 */
-		if (is_atomic &&
-		    sclk->info->enable_latency <= atomic_threshold)
+		if (sclk->info->state_ctrl_forbidden)
+			scmi_ops = &scmi_no_state_ctrl_clk_ops;
+		else if (is_atomic &&
+			 sclk->info->enable_latency <= atomic_threshold)
 			scmi_ops = &scmi_atomic_clk_ops;
 		else
 			scmi_ops = &scmi_clk_ops;
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index f0940af485a5..79b90a8099d7 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1200,9 +1200,11 @@ void clk_gate_restore_context(struct clk_hw *hw)
 	struct clk_core *core = hw->core;
 
 	if (core->enable_count)
-		core->ops->enable(hw);
+		if (core->ops->enable)
+			core->ops->enable(hw);
 	else
-		core->ops->disable(hw);
+		if (core->ops->disable)
+			core->ops->disable(hw);
 }
 EXPORT_SYMBOL_GPL(clk_gate_restore_context);
---8<---

> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
> 
> V3:
>  Add check in atomic enable
> 
> V2:
>  New. Take Cristian's suggestion
> 
>  drivers/clk/clk-scmi.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c
> index 8cbe24789c24..5327e0547741 100644
> --- a/drivers/clk/clk-scmi.c
> +++ b/drivers/clk/clk-scmi.c
> @@ -119,8 +119,13 @@ static int scmi_clk_determine_rate(struct clk_hw *hw, struct clk_rate_request *r
>  static int scmi_clk_enable(struct clk_hw *hw)
>  {
>  	struct scmi_clk *clk = to_scmi_clk(hw);
> +	int ret;
> +
> +	ret = scmi_proto_clk_ops->enable(clk->ph, clk->id, NOT_ATOMIC);
> +	if (ret == -EACCES && clk->info->state_ctrl_forbidden)
> +		return 0;
>  
> -	return scmi_proto_clk_ops->enable(clk->ph, clk->id, NOT_ATOMIC);
> +	return ret;
>  }
>  
>  static void scmi_clk_disable(struct clk_hw *hw)
> @@ -133,8 +138,13 @@ static void scmi_clk_disable(struct clk_hw *hw)
>  static int scmi_clk_atomic_enable(struct clk_hw *hw)
>  {
>  	struct scmi_clk *clk = to_scmi_clk(hw);
> +	int ret;
> +
> +	ret = scmi_proto_clk_ops->enable(clk->ph, clk->id, ATOMIC);
> +	if (ret == -EACCES && clk->info->state_ctrl_forbidden)
> +		return 0;
>  
> -	return scmi_proto_clk_ops->enable(clk->ph, clk->id, ATOMIC);
> +	return ret;
>  }
>  
>  static void scmi_clk_atomic_disable(struct clk_hw *hw)
> -- 
> 2.37.1
>