linux-kernel - Re: [PATCH] drivers: dma: qcom: bam_dma: Manage clocks when controlled

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Message-ID: <20210122051013.GE2479@dragon>
Date:   Fri, 22 Jan 2021 13:10:14 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     agross@...nel.org, bjorn.andersson@...aro.org,
        dan.j.williams@...el.com, vkoul@...nel.org,
        srinivas.kandagatla@...aro.org, linux-arm-msm@...r.kernel.org,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: dma: qcom: bam_dma: Manage clocks when
 controlled_remotely is set

On Thu, Jan 21, 2021 at 09:52:51PM -0500, Thara Gopinath wrote:
> When bam dma is "controlled remotely", thus far clocks were not controlled
> from the Linux. In this scenario, Linux was disabling runtime pm in bam dma
> driver and not doing any clock management in suspend/resume hooks.
> 
> With introduction of crypto engine bam dma, the clock is a rpmh resource
> that can be controlled from both Linux and TZ/remote side.  Now bam dma
> clock is getting enabled during probe even though the bam dma can be
> "controlled remotely". But due to clocks not being handled properly,
> bam_suspend generates a unbalanced clk_unprepare warning during system
> suspend.
> 
> To fix the above issue and to enable proper clock-management, this patch
> enables runtim-pm and handles bam dma clocks in suspend/resume hooks if
> the clock node is present irrespective of controlled_remotely property.

Shouldn't the following probe code need some update?  Now we have both
controlled_remotely and clocks handle for cryptobam node.  For example,
if devm_clk_get() returns -EPROBE_DEFER, we do not want to continue with
bamclk forcing to be NULL, right?

        bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
        if (IS_ERR(bdev->bamclk)) {
                if (!bdev->controlled_remotely)
                        return PTR_ERR(bdev->bamclk);

                bdev->bamclk = NULL;
        }

> 
> Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
> ---
>  drivers/dma/qcom/bam_dma.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 88579857ca1d..b3a34be63e99 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -1350,7 +1350,7 @@ static int bam_dma_probe(struct platform_device *pdev)
>  	if (ret)
>  		goto err_unregister_dma;
>  
> -	if (bdev->controlled_remotely) {
> +	if (!bdev->bamclk) {
>  		pm_runtime_disable(&pdev->dev);
>  		return 0;
>  	}
> @@ -1438,10 +1438,10 @@ static int __maybe_unused bam_dma_suspend(struct device *dev)
>  {
>  	struct bam_device *bdev = dev_get_drvdata(dev);
>  
> -	if (!bdev->controlled_remotely)
> +	if (bdev->bamclk) {
>  		pm_runtime_force_suspend(dev);
> -
> -	clk_unprepare(bdev->bamclk);
> +		clk_unprepare(bdev->bamclk);
> +	}
>  
>  	return 0;
>  }
> @@ -1451,12 +1451,14 @@ static int __maybe_unused bam_dma_resume(struct device *dev)
>  	struct bam_device *bdev = dev_get_drvdata(dev);
>  	int ret;
>  
> -	ret = clk_prepare(bdev->bamclk);
> -	if (ret)
> -		return ret;
> +	if (bdev->bamclk) {
> +		ret = clk_prepare(bdev->bamclk);
> +		if (ret)
> +			return ret;
>  
> -	if (!bdev->controlled_remotely)
> -		pm_runtime_force_resume(dev);
> +		if (!bdev->controlled_remotely)

Why do we still need controlled_remotely check here?

Shawn

> +			pm_runtime_force_resume(dev);
> +	}
>  
>  	return 0;
>  }
> -- 
> 2.25.1
>