Re: [PATCH] drm/msm/dpu: Don't use devm for component devices

[Jeykumar Sankaran <jsanka@xxxxxxxxxxxxxx>]

On 2018-11-02 07:30, Jordan Crouse wrote:
> Devices that are bound as components should not use devm since
> device managed memory is not freed when the component is
> unbound.
>
> In particular this is an issue if the component bind fails
> due to an -EPROBE_DEFER. In this case the bind would try again

Isn't this the only case where using devm would be a problem? Even in 
this case
do you expect any leaks if devm_kfree is called before DEFERing due to 
errors
and in unbounds?

Thanks,
Jeykumar S.
> later and any devm managed memory allocated during the former
> aborted attempt would be leaked until the device itself was
> destroyed. Since all the memory allocated during a bind
> should be freed during an unbind (or bind error case) there isn't
> any reason to use devm for resources that have a explicit
> teardown step.
>
> This doesn't remove devm for all resources - in particular
> msm_ioremap() still uses devm_ioremap() but thats a generic
> issue that can easily be addressed as a cleanup later and the
> unbind code already does the requisite devm calls to unmap it.
>
> Signed-off-by: Jordan Crouse <jcrouse@xxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c |  4 ++--
>  drivers/gpu/drm/msm/disp/dpu1/dpu_io_util.c |  4 +---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c     | 10 ++++++----
>  drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c    |  8 +++++---
>  4 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> index 82c55efb500f..287d4c3e58c3 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> @@ -2220,14 +2220,14 @@ struct drm_encoder *dpu_encoder_init(struct
> drm_device *dev,
>  	struct dpu_encoder_virt *dpu_enc = NULL;
>  	int rc = 0;
>
> -	dpu_enc = devm_kzalloc(dev->dev, sizeof(*dpu_enc), GFP_KERNEL);
> +	dpu_enc = kzalloc(sizeof(*dpu_enc), GFP_KERNEL);
>  	if (!dpu_enc)
>  		return ERR_PTR(ENOMEM);
>
>  	rc = drm_encoder_init(dev, &dpu_enc->base, &dpu_encoder_funcs,
>  			drm_enc_mode, NULL);
>  	if (rc) {
> -		devm_kfree(dev->dev, dpu_enc);
> +		kfree(dpu_enc);
>  		return ERR_PTR(rc);
>  	}
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_io_util.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_io_util.c
> index 89ee4b36beff..90b53e9508f2 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_io_util.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_io_util.c
> @@ -155,9 +155,7 @@ int msm_dss_parse_clock(struct platform_device 
> *pdev,
>  		return 0;
>  	}
>
> -	mp->clk_config = devm_kzalloc(&pdev->dev,
> -				      sizeof(struct dss_clk) * num_clk,
> -				      GFP_KERNEL);
> +	mp->clk_config = kcalloc(num_clk, sizeof(struct dss_clk), 
> GFP_KERNEL);
>  	if (!mp->clk_config)
>  		return -ENOMEM;
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index 985c855796ae..5ac3c3f3b08d 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -1086,13 +1086,14 @@ static int dpu_bind(struct device *dev, struct
> device *master, void *data)
>  	struct dss_module_power *mp;
>  	int ret = 0;
>
> -	dpu_kms = devm_kzalloc(&pdev->dev, sizeof(*dpu_kms), GFP_KERNEL);
> +	dpu_kms = kzalloc(sizeof(*dpu_kms), GFP_KERNEL);
>  	if (!dpu_kms)
>  		return -ENOMEM;
>
>  	mp = &dpu_kms->mp;
>  	ret = msm_dss_parse_clock(pdev, mp);
>  	if (ret) {
> +		kfree(dpu_kms);
>  		DPU_ERROR("failed to parse clocks, ret=%d\n", ret);
>  		return ret;
>  	}
> @@ -1109,7 +1110,7 @@ static int dpu_bind(struct device *dev, struct 
> device
> *master, void *data)
>  	dpu_kms->rpm_enabled = true;
>
>  	priv->kms = &dpu_kms->base;
> -	return ret;
> +	return 0;
>  }
>
>  static void dpu_unbind(struct device *dev, struct device *master, void
> *data)
> @@ -1120,11 +1121,12 @@ static void dpu_unbind(struct device *dev, 
> struct
> device *master, void *data)
>
>  	dpu_power_resource_deinit(pdev, &dpu_kms->phandle);
>  	msm_dss_put_clk(mp->clk_config, mp->num_clk);
> -	devm_kfree(&pdev->dev, mp->clk_config);
> -	mp->num_clk = 0;
> +	kfree(mp->clk_config);
>
>  	if (dpu_kms->rpm_enabled)
>  		pm_runtime_disable(&pdev->dev);
> +
> +	kfree(dpu_kms);
>  }
>
>  static const struct component_ops dpu_ops = {
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> index 2235ef8129f4..34ab489b1a5b 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_mdss.c
> @@ -161,7 +161,7 @@ static void dpu_mdss_destroy(struct drm_device 
> *dev)
>  	free_irq(platform_get_irq(pdev, 0), dpu_mdss);
>
>  	msm_dss_put_clk(mp->clk_config, mp->num_clk);
> -	devm_kfree(&pdev->dev, mp->clk_config);
> +	kfree(mp->clk_config);
>
>  	if (dpu_mdss->mmio)
>  		devm_iounmap(&pdev->dev, dpu_mdss->mmio);
> @@ -169,6 +169,8 @@ static void dpu_mdss_destroy(struct drm_device 
> *dev)
>
>  	pm_runtime_disable(dev->dev);
>  	priv->mdss = NULL;
> +
> +	kfree(dpu_mdss);
>  }
>
>  static const struct msm_mdss_funcs mdss_funcs = {
> @@ -186,7 +188,7 @@ int dpu_mdss_init(struct drm_device *dev)
>  	struct dss_module_power *mp;
>  	int ret = 0;
>
> -	dpu_mdss = devm_kzalloc(dev->dev, sizeof(*dpu_mdss), GFP_KERNEL);
> +	dpu_mdss = kzalloc(sizeof(*dpu_mdss), GFP_KERNEL);
>  	if (!dpu_mdss)
>  		return -ENOMEM;
>
> @@ -239,7 +241,7 @@ int dpu_mdss_init(struct drm_device *dev)
>  irq_domain_error:
>  	msm_dss_put_clk(mp->clk_config, mp->num_clk);
>  clk_parse_err:
> -	devm_kfree(&pdev->dev, mp->clk_config);
> +	kfree(mp->clk_config);
>  	if (dpu_mdss->mmio)
>  		devm_iounmap(&pdev->dev, dpu_mdss->mmio);
>  	dpu_mdss->mmio = NULL;

--
Jeykumar S