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[PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support using managed version

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  [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support using  managed version Shraddha Barke <shraddha.6596@gmail.com> - 2016-02-12 08:30 +0100
    Re: [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support  using managed version Joe Perches <joe@perches.com> - 2016-02-12 11:20 +0100

#1332555 — [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support using managed version

setup_access_params_addr has 2 goals-

-Initialize the access_params field so that it can be used to send and read
commands from the device in access_with_param
-Get a bus address for the allocated memory to transfer to the device.

Replace the combination of devm_kzalloc and _pa() with dmam_alloc_coherent.
Coherent mapping guarantees that the device and CPU are in sync.

Signed-off-by: Shraddha Barke <shraddha.6596@gmail.com>
---
 drivers/platform/goldfish/goldfish_pipe.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
index e7a29e2..49f877d 100644
--- a/drivers/platform/goldfish/goldfish_pipe.c
+++ b/drivers/platform/goldfish/goldfish_pipe.c
@@ -57,6 +57,7 @@
 #include <linux/slab.h>
 #include <linux/io.h>
 #include <linux/goldfish.h>
+#include <linux/dma-mapping.h>
 
 /*
  * IMPORTANT: The following constants must match the ones used and defined
@@ -217,17 +218,18 @@ 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");
+		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(upper_32_bits(dma_handle), dev->base + PIPE_REG_PARAMS_ADDR_HIGH);
+	writel(lower_32_bits(dma_handle), dev->base + PIPE_REG_PARAMS_ADDR_LOW);
 
 	if (valid_batchbuffer_addr(dev, aps)) {
 		dev->aps = aps;
-- 
2.1.4

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#1332660 — Re: [PATCH] Platform: goldfish: goldfish_pipe.c: Add DMA support using managed version

On Fri, 2016-02-12 at 12:53 +0530, Shraddha Barke wrote:
> setup_access_params_addr has 2 goals-
> 
> -Initialize the access_params field so that it can be used to send and read
> commands from the device in access_with_param
> -Get a bus address for the allocated memory to transfer to the device.
> 
> Replace the combination of devm_kzalloc and _pa() with dmam_alloc_coherent.

trivia:

> diff --git a/drivers/platform/goldfish/goldfish_pipe.c b/drivers/platform/goldfish/goldfish_pipe.c
[]
> @@ -217,17 +218,18 @@ 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");

This is still an unnecessary allocation failure message.
There's already a generic OOM message and stack dump emitted.

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