linux-kernel - Re: [PATCH v2 2/3] drivers: dma-coherent: add initialization from device tree

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Date:	Wed, 24 Sep 2014 15:26:06 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Marek Szyprowski <m.szyprowski@...sung.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-mm-sig@...ts.linaro.org, Arnd Bergmann <arnd@...db.de>,
	Michal Nazarewicz <mina86@...a86.com>,
	Grant Likely <grant.likely@...aro.org>,
	Laura Abbott <lauraa@...eaurora.org>,
	Josh Cartwright <joshc@...eaurora.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Kyungmin Park <kyungmin.park@...sung.com>
Subject: Re: [PATCH v2 2/3] drivers: dma-coherent: add initialization from
 device tree

On Thu, 11 Sep 2014 13:22:40 +0200 Marek Szyprowski <m.szyprowski@...sung.com> wrote:

> Initialization procedure of dma coherent pool has been split into two
> parts, so memory pool can now be initialized without assigning to
> particular struct device. Then initialized region can be assigned to
> more than one struct device. To protect from concurent allocations from
> different devices, a spinlock has been added to dma_coherent_mem
> structure. The last part of this patch adds support for handling
> 'shared-dma-pool' reserved-memory device tree nodes.
> 
> --- a/drivers/base/dma-coherent.c
> +++ b/drivers/base/dma-coherent.c
> @@ -14,11 +14,14 @@ struct dma_coherent_mem {
>  	int		size;
>  	int		flags;
>  	unsigned long	*bitmap;
> +	spinlock_t	spinlock;

A bit of documentation would be nice: explain what the lock protects,
that it is irq-safe, etc.

>  };
>  
> -int dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
> -				dma_addr_t device_addr, size_t size, int flags)
> +static int dma_init_coherent_memory(phys_addr_t phys_addr, dma_addr_t device_addr,
> +			     size_t size, int flags,
> +			     struct dma_coherent_mem **mem)
>  {
> +	struct dma_coherent_mem *dma_mem = NULL;

The only reason to initialise this is so we can kfree() it without
checking.  In which case we don't need label free1_out?

--- a/drivers/base/dma-coherent.c~drivers-dma-coherent-add-initialization-from-device-tree-fix
+++ a/drivers/base/dma-coherent.c
@@ -40,7 +40,7 @@ static int dma_init_coherent_memory(phys
 		goto out;
 	dma_mem->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
 	if (!dma_mem->bitmap)
-		goto free1_out;
+		goto out;
 
 	dma_mem->virt_base = mem_base;
 	dma_mem->device_base = device_addr;
@@ -56,9 +56,8 @@ static int dma_init_coherent_memory(phys
 
 	return DMA_MEMORY_IO;
 
- free1_out:
+out:
 	kfree(dma_mem);
- out:
 	if (mem_base)
 		iounmap(mem_base);
 	return 0;
_

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