linux-kernel - Re: [PATCH v2 1/2] clk: qcom: common: Add API to register board clocks backwards compatibly

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Message-ID: <56310DDC.6010000@linaro.org>
Date:	Wed, 28 Oct 2015 20:03:08 +0200
From:	Georgi Djakov <georgi.djakov@...aro.org>
To:	Stephen Boyd <sboyd@...eaurora.org>,
	Mike Turquette <mturquette@...libre.com>
Cc:	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 1/2] clk: qcom: common: Add API to register board
 clocks backwards compatibly

On 10/28/2015 03:06 AM, Stephen Boyd wrote:
> On 10/27, Stephen Boyd wrote:
>> +
>> +int qcom_cc_register_board_clk(struct device *dev, const char *path,
>> +			       const char *name, unsigned long rate)
>> +{
>> +	return _qcom_cc_register_board_clk(dev, path, name, rate,
>> +					   !IS_ENABLED(CONFIG_QCOM_RPMCC));
> 
> I just realized that we could have this config enabled but the
> driver never probes on a certain platform. So we'll need to do
> some sort of search to see if the rpmcc node exists and also
> check to see if the driver is enabled. I guess we can do that all
> here in this function as long as we have a compatible =
> "qcom,rpmcc" as a more generic property for the rpm clock
> controller node. So if the config is enabled, search the dt tree
> for a qcom,rpmcc node. If the rpmcc node is there, the last
> argument is false, otherwise it's true.

I like the approach.  We could have both compatible strings like:
compatible = "qcom,rpmcc-msm8916", "qcom,rpmcc";

The only possible issue i could imagine is the case when rpmcc
driver probe fails - does not enable scaling for example. Then we
will be left without xo. But maybe we should not handle this
scenario anyway.

> 
> ---8<----
> diff --git a/drivers/clk/qcom/common.c b/drivers/clk/qcom/common.c
> index 572851b5bc16..215a41ba0135 100644
> --- a/drivers/clk/qcom/common.c
> +++ b/drivers/clk/qcom/common.c
> @@ -17,6 +17,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/clk-provider.h>
>  #include <linux/reset-controller.h>
> +#include <linux/of.h>
>  
>  #include "common.h"
>  #include "clk-rcg.h"
> @@ -152,7 +153,18 @@ static int _qcom_cc_register_board_clk(struct device *dev, const char *path,
>  int qcom_cc_register_board_clk(struct device *dev, const char *path,
>  			       const char *name, unsigned long rate)
>  {
> -	return _qcom_cc_register_board_clk(dev, path, name, rate, true);
> +	bool add_factor = true;
> +	struct device_node *node;
> +
> +	/* The RPM clock driver will add the factor clock if present */
> +	if (IS_ENABLED(CONFIG_QCOM_RPMCC)) {
> +		node = of_find_compatible_node(NULL, NULL, "qcom,rpmcc");
> +		if (node)

if (node && of_device_is_available(node))
to handle also the case with status="disabled"

> +			add_factor = false;
> +		of_node_put(node);
> +	}
> +
> +	return _qcom_cc_register_board_clk(dev, path, name, rate, add_factor);
>  }
>  EXPORT_SYMBOL_GPL(qcom_cc_register_board_clk);
>  
> 

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