linux-kernel - Re: [PATCH 09/46] dmaengine: cppi41: use dmaenginem_async_device

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Message-ID: <43458794-d124-13df-c944-e473dc8ee1c2@ti.com>
Date:   Fri, 3 Aug 2018 10:55:25 +0300
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Huang Shijie <sjhuang@...vatar.ai>, <vkoul@...nel.org>
CC:     <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <dave.jiang@...el.com>, <radhey.shyam.pandey@...inx.com>,
        <appana.durga.rao@...inx.com>, <jmkrzyszt@...il.com>,
        <gomonovych@...il.com>, <keescook@...omium.org>,
        <horms+renesas@...ge.net.au>, <geert+renesas@...der.be>,
        <shawnguo@...nel.org>, <baoyou.xie@...aro.org>,
        <michal.simek@...inx.com>, <baohua@...nel.org>,
        <ludovic.desroches@...rochip.com>, <linus.walleij@...aro.org>,
        <david.brown@...aro.org>
Subject: Re: [PATCH 09/46] dmaengine: cppi41: use
 dmaenginem_async_device_register to simplify the code



On 2018-08-03 10:19, Huang Shijie wrote:
> Use dmaenginem_async_device_register to simplify the code:
>    remove dma_async_device_unregister
> 
> Signed-off-by: Huang Shijie <sjhuang@...vatar.ai>
> ---
>  drivers/dma/ti/cppi41.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/dma/ti/cppi41.c b/drivers/dma/ti/cppi41.c
> index 1497da367710..d2998a19ed2e 100644
> --- a/drivers/dma/ti/cppi41.c
> +++ b/drivers/dma/ti/cppi41.c
> @@ -1096,21 +1096,19 @@ static int cppi41_dma_probe(struct platform_device *pdev)
>  		goto err_chans;
>  	cdd->irq = irq;
>  
> -	ret = dma_async_device_register(&cdd->ddev);
> +	ret = dmaenginem_async_device_register(&cdd->ddev);
>  	if (ret)
>  		goto err_chans;
>  
>  	ret = of_dma_controller_register(dev->of_node,
>  			cppi41_dma_xlate, &cpp41_dma_info);
>  	if (ret)
> -		goto err_of;
> +		goto err_chans;
>  
>  	pm_runtime_mark_last_busy(dev);
>  	pm_runtime_put_autosuspend(dev);
>  
>  	return 0;
> -err_of:
> -	dma_async_device_unregister(&cdd->ddev);
>  err_chans:
>  	deinit_cppi41(dev, cdd);
>  err_init_cppi:
> @@ -1132,7 +1130,6 @@ static int cppi41_dma_remove(struct platform_device *pdev)
>  		dev_err(&pdev->dev, "%s could not pm_runtime_get: %i\n",
>  			__func__, error);
>  	of_dma_controller_free(pdev->dev.of_node);
> -	dma_async_device_unregister(&cdd->ddev);

If I read the code right then this is not safe.
We would have deinitalized cppi41 driver which is not functional, but we
will still have the dma device registered and if a channel is requested
we will have kernel crash.

It falls in the same case as omap-dma, edma.

>  
>  	devm_free_irq(&pdev->dev, cdd->irq, cdd);
>  	deinit_cppi41(&pdev->dev, cdd);
> 

- Péter

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