linux-kernel - Re: [PATCH v2 5/5] clk: qcom: ipq4019: Added the cpu clock frequency change notifier

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Date:	Mon, 15 Aug 2016 15:26:14 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Abhishek Sahu <absahu@...eaurora.org>
Cc:	andy.gross@...aro.org, david.brown@...aro.org, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, mturquette@...libre.com,
	galak@...eaurora.org, pradeepb@...eaurora.org,
	mmcclint@...eaurora.org, varada@...eaurora.org,
	sricharan@...eaurora.org, architt@...eaurora.org,
	ntelkar@...eaurora.org, linux-arm-msm@...r.kernel.org,
	linux-soc@...r.kernel.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 5/5] clk: qcom: ipq4019: Added the cpu clock frequency
 change notifier

On 06/21, Abhishek Sahu wrote:
> The current driver code gives the crash or gets hang while switching
> the CPU frequency some time. The APSS CPU Clock divider is not glitch
> free so it the APPS clock need to be switched for stable clock during
> the change.
> 
> This patch adds the frequency change notifier for APSS CPU clock. It
> changes the parent of this clock to stable PLL FEPLL500 when it gets
> for PRE_RATE_CHANGE event. This event will be generated before actual
> clock set operations. The clock set operation will again change its
> corresponding parent by getting the same from frequency table.
> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>  drivers/clk/qcom/gcc-ipq4019.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/qcom/gcc-ipq4019.c b/drivers/clk/qcom/gcc-ipq4019.c
> index df159c2..3c014f7 100644
> --- a/drivers/clk/qcom/gcc-ipq4019.c
> +++ b/drivers/clk/qcom/gcc-ipq4019.c
> @@ -1740,9 +1740,34 @@ static const struct of_device_id gcc_ipq4019_match_table[] = {
>  };
>  MODULE_DEVICE_TABLE(of, gcc_ipq4019_match_table);
>  
> +int cpu_clk_notifier_fn(struct notifier_block *nb,

static?

Please come up with a better name that is not so generic.

> +			unsigned long action, void *data)
> +{
> +	int err = 0;
> +
> +	if (action == PRE_RATE_CHANGE) {
> +		err = clk_rcg2_ops.set_parent(&apps_clk_src.clkr.hw,
> +							P_FEPLL500);
> +	}
> +
> +	return notifier_from_errno(err);
> +}
> +
> +struct notifier_block cpu_clk_notifier = {

static?

> +	.notifier_call = cpu_clk_notifier_fn,
> +};
> +
>  static int gcc_ipq4019_probe(struct platform_device *pdev)
>  {
> -	return qcom_cc_probe(pdev, &gcc_ipq4019_desc);
> +	int err;
> +
> +	err = qcom_cc_probe(pdev, &gcc_ipq4019_desc);
> +
> +	if (!err)
> +		clk_notifier_register(apps_clk_src.clkr.hw.clk,
> +					&cpu_clk_notifier);

This has to be unregistered on driver remove.

> +
> +	return err;
>  }

-- 
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