linux-kernel - Re: [PATCH v2] dma: qcom: bam_dma: Manage clocks when controlled

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Date:   Tue, 26 Jan 2021 23:33:38 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     agross@...nel.org, dan.j.williams@...el.com, vkoul@...nel.org,
        shawn.guo@...aro.org, srinivas.kandagatla@...aro.org,
        linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] dma: qcom: bam_dma: Manage clocks when
 controlled_remotely is set

On Tue 26 Jan 15:18 CST 2021, 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.
> 
> Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>


And from John on IRC:

Tested-by: John Stultz <john.stultz@...aro.org>

Regards,
Bjorn

> ---
> 
> v1->v2:
> 	- As per Shawn's suggestion, use devm_clk_get_optional to get the
> 	  bam clock if the "controlled_remotely" property is set so that
> 	  the clock code takes care of setting the bam clock to NULL if
> 	  not specified by dt. 
> 	- Remove the check for "controlled_remotely" property in
> 	  bam_dma_resume now that clock enable / disable is based on
> 	  whether bamclk is NULL or not.
> 	- Rebased to v5.11-rc5
> 
>  drivers/dma/qcom/bam_dma.c | 29 +++++++++++++++--------------
>  1 file changed, 15 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 88579857ca1d..c8a77b428b52 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -1270,13 +1270,13 @@ static int bam_dma_probe(struct platform_device *pdev)
>  			dev_err(bdev->dev, "num-ees unspecified in dt\n");
>  	}
>  
> -	bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
> -	if (IS_ERR(bdev->bamclk)) {
> -		if (!bdev->controlled_remotely)
> -			return PTR_ERR(bdev->bamclk);
> +	if (bdev->controlled_remotely)
> +		bdev->bamclk = devm_clk_get_optional(bdev->dev, "bam_clk");
> +	else
> +		bdev->bamclk = devm_clk_get(bdev->dev, "bam_clk");
>  
> -		bdev->bamclk = NULL;
> -	}
> +	if (IS_ERR(bdev->bamclk))
> +		return PTR_ERR(bdev->bamclk);
>  
>  	ret = clk_prepare_enable(bdev->bamclk);
>  	if (ret) {
> @@ -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 +1451,13 @@ 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);
> +	}
>  
>  	return 0;
>  }
> -- 
> 2.25.1
>