linux-kernel - Re: [PATCH] clk: tegra: dfll: Fix drvdata overwriting issue

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Message-ID: <20171019075129.GO27164@tbergstrom-lnx.Nvidia.com>
Date:   Thu, 19 Oct 2017 10:51:29 +0300
From:   Peter De Schrijver <pdeschrijver@...dia.com>
To:     Nicolin Chen <nicoleotsuka@...il.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <jonathanh@...dia.com>,
        <thierry.reding@...il.com>, <sboyd@...eaurora.org>,
        <mturquette@...libre.com>, <pgaikwad@...dia.com>
Subject: Re: [PATCH] clk: tegra: dfll: Fix drvdata overwriting issue

On Thu, Oct 12, 2017 at 04:09:59PM -0700, Nicolin Chen wrote:
> Both tegra124-dfll and clk-dfll are using platform_set_drvdata
> to set drvdata of the exact same pdev while they use different
> pointers for the drvdata. Once the drvdata has been overwritten
> by tegra124-dfll, clk-dfll will never get its td pointer as it
> expects.
> 
> Since tegra124-dfll merely needs its soc pointer in its remove
> function, this patch fixes the bug by removing the overwriting
> in the tegra124-dfll file and letting the tegra_dfll_unregister
> return an soc pointer for it.
> 
> Signed-off-by: Nicolin Chen <nicoleotsuka@...il.com>

Acked-By: Peter De Schrijver <pdeschrijver@...dia.com>

> ---
> 
> As I don't have a T124 platform, I can't verify it on a board.
> If someone could provide a Tested-by, it would be very helpful.
> The test could be a simple system suspend/resume that activates
> runtime_suspend/resume() where a platform_get_drvdata() would
> be called. -- Nicolin
> 
>  drivers/clk/tegra/clk-dfll.c               | 10 +++++-----
>  drivers/clk/tegra/clk-dfll.h               |  2 +-
>  drivers/clk/tegra/clk-tegra124-dfll-fcpu.c | 12 +++++-------
>  3 files changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll.c
> index 2c44aeb..0a7deee 100644
> --- a/drivers/clk/tegra/clk-dfll.c
> +++ b/drivers/clk/tegra/clk-dfll.c
> @@ -1728,10 +1728,10 @@ EXPORT_SYMBOL(tegra_dfll_register);
>   * @pdev: DFLL platform_device *
>   *
>   * Unbind this driver from the DFLL hardware device represented by
> - * @pdev. The DFLL must be disabled for this to succeed. Returns 0
> - * upon success or -EBUSY if the DFLL is still active.
> + * @pdev. The DFLL must be disabled for this to succeed. Returns a
> + * soc pointer upon success or -EBUSY if the DFLL is still active.
>   */
> -int tegra_dfll_unregister(struct platform_device *pdev)
> +struct tegra_dfll_soc_data *tegra_dfll_unregister(struct platform_device *pdev)
>  {
>  	struct tegra_dfll *td = platform_get_drvdata(pdev);
>  
> @@ -1739,7 +1739,7 @@ int tegra_dfll_unregister(struct platform_device *pdev)
>  	if (td->mode != DFLL_DISABLED) {
>  		dev_err(&pdev->dev,
>  			"must disable DFLL before removing driver\n");
> -		return -EBUSY;
> +		return ERR_PTR(-EBUSY);
>  	}
>  
>  	debugfs_remove_recursive(td->debugfs_dir);
> @@ -1753,6 +1753,6 @@ int tegra_dfll_unregister(struct platform_device *pdev)
>  
>  	reset_control_assert(td->dvco_rst);
>  
> -	return 0;
> +	return td->soc;
>  }
>  EXPORT_SYMBOL(tegra_dfll_unregister);
> diff --git a/drivers/clk/tegra/clk-dfll.h b/drivers/clk/tegra/clk-dfll.h
> index ed2ad88..83352c8 100644
> --- a/drivers/clk/tegra/clk-dfll.h
> +++ b/drivers/clk/tegra/clk-dfll.h
> @@ -43,7 +43,7 @@ struct tegra_dfll_soc_data {
>  
>  int tegra_dfll_register(struct platform_device *pdev,
>  			struct tegra_dfll_soc_data *soc);
> -int tegra_dfll_unregister(struct platform_device *pdev);
> +struct tegra_dfll_soc_data *tegra_dfll_unregister(struct platform_device *pdev);
>  int tegra_dfll_runtime_suspend(struct device *dev);
>  int tegra_dfll_runtime_resume(struct device *dev);
>  
> diff --git a/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c b/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c
> index ad1c1cc..269d359 100644
> --- a/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c
> +++ b/drivers/clk/tegra/clk-tegra124-dfll-fcpu.c
> @@ -125,19 +125,17 @@ static int tegra124_dfll_fcpu_probe(struct platform_device *pdev)
>  		return err;
>  	}
>  
> -	platform_set_drvdata(pdev, soc);
> -
>  	return 0;
>  }
>  
>  static int tegra124_dfll_fcpu_remove(struct platform_device *pdev)
>  {
> -	struct tegra_dfll_soc_data *soc = platform_get_drvdata(pdev);
> -	int err;
> +	struct tegra_dfll_soc_data *soc;
>  
> -	err = tegra_dfll_unregister(pdev);
> -	if (err < 0)
> -		dev_err(&pdev->dev, "failed to unregister DFLL: %d\n", err);
> +	soc = tegra_dfll_unregister(pdev);
> +	if (IS_ERR(soc))
> +		dev_err(&pdev->dev, "failed to unregister DFLL: %ld\n",
> +			PTR_ERR(soc));
>  
>  	tegra_cvb_remove_opp_table(soc->dev, soc->cvb, soc->max_freq);
>  
> -- 
> 2.1.4
> 
> --
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