linux-kernel - Re: [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support using managed version

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Date:	Fri, 22 Jan 2016 11:58:11 -0800
From:	Joe Perches <joe@...ches.com>
To:	Shraddha Barke <shraddha.6596@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-kernel@...r.kernel.org
Cc:	Peter Senna Tschudin <peter.senna@...il.com>,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support
 using managed version

On Sat, 2016-01-23 at 01:21 +0530, Shraddha Barke wrote:
> Function setup_access_params_addr is called only from probe function, hence
> managed version dmam_alloc_coherent is used.

trivia:

> diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
[]
> @@ -217,17 +218,19 @@ static int valid_batchbuffer_addr(struct goldfish_pipe_dev *dev,
>  static int setup_access_params_addr(struct platform_device *pdev,
>  					struct goldfish_pipe_dev *dev)
>  {
> -	u64 paddr;
> +	dma_addr_t dma_handle;
>  	struct access_params *aps;
>  
> -	aps = devm_kzalloc(&pdev->dev, sizeof(struct access_params), GFP_KERNEL);
> -	if (!aps)
> -		return -1;
> +	aps = dmam_alloc_coherent(&pdev->dev, sizeof(struct access_params),
> +				  &dma_handle, GFP_KERNEL);
> +	if (!aps) {
> +		dev_err(&pdev->dev, "allocate buffer failed\n");

Unnecessary error message

> +		return -ENOMEM;
> +	}
>  
> -	/* FIXME */
> -	paddr = __pa(aps);
> -	writel((u32)(paddr >> 32), dev->base + PIPE_REG_PARAMS_ADDR_HIGH);
> -	writel((u32)paddr, dev->base + PIPE_REG_PARAMS_ADDR_LOW);
> +	writel((u32)((u64)dma_handle >> 32), dev->base +
> +		PIPE_REG_PARAMS_ADDR_HIGH);
> +	writel((u32)dma_handle, dev->base + PIPE_REG_PARAMS_ADDR_LOW);

Probably better to use upper_32_bits and lower_32_bits