linux-kernel - Re: [PATCH v2] clk: Do not complain about correctly set read-only muxes when assigning clock parents from device tree

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Date:	Thu, 08 Jan 2015 13:32:56 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Philipp Zabel <p.zabel@...gutronix.de>,
	Mike Turquette <mturquette@...aro.org>
CC:	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH v2] clk: Do not complain about correctly set read-only
 muxes when assigning clock parents from device tree

On 01/06/2015 07:45 AM, Philipp Zabel wrote:
> diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c
> index aad4796..bb4dc02 100644
> --- a/drivers/clk/clk-conf.c
> +++ b/drivers/clk/clk-conf.c
> @@ -62,10 +62,13 @@ static int __set_clk_parents(struct device_node *node, bool clk_supplier)
>  			goto err;
>  		}
>  
> -		rc = clk_set_parent(clk, pclk);
> -		if (rc < 0)
> -			pr_err("clk: failed to reparent %s to %s: %d\n",
> -			       __clk_get_name(clk), __clk_get_name(pclk), rc);
> +		if (pclk != __clk_get_parent(clk)) {
> +			rc = clk_set_parent(clk, pclk);
> +			if (rc < 0)
> +				pr_err("clk: failed to reparent %s to %s: %d\n",
> +				       __clk_get_name(clk),
> +				       __clk_get_name(pclk), rc);
> +		}
>  		clk_put(clk);
>  		clk_put(pclk);
>  	}

Why not do this in the core? As far as I can tell other drivers could
run into the same problem, no? Does this work?

-----8<-------

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index f4963b7d4e17..3278645f4729 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1677,16 +1677,18 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 	if (!clk)
 		return 0;
 
-	/* verify ops for for multi-parent clks */
-	if ((clk->num_parents > 1) && (!clk->ops->set_parent))
-		return -ENOSYS;
-
 	/* prevent racing with updates to the clock topology */
 	clk_prepare_lock();
 
 	if (clk->parent == parent)
 		goto out;
 
+	/* verify ops for for multi-parent clks */
+	if ((clk->num_parents > 1) && (!clk->ops->set_parent)) {
+		ret = -ENOSYS;
+		goto out;
+	}
+
 	/* check that we are allowed to re-parent if the clock is in use */
 	if ((clk->flags & CLK_SET_PARENT_GATE) && clk->prepare_count) {
 		ret = -EBUSY;

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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