Commit ccac0515 authored by Stephen Warren's avatar Stephen Warren Committed by Colin Cross
Browse files

ARM: Tegra: DMA: Fail safe if initialization fails 



tegra_dma_init currently simply bails out early if any initialization fails.
This skips various data-structure initialization. In turn, this means that
tegra_dma_allocate_channel can still hand out channels. In this case, when
tegra_dma_free_channel is called, which calls tegra_dma_cancel, the walking
on ch->list will OOPS since the list's next/prev pointers may still be
NULL.

To solve this, add an explicit "initialized" flag, only set this once _init
has fully completed successfully, and have _allocate_channel refuse to hand
out channels if this is not set.

While at it, simplify _init:
* Remove redundant memsets
* Use bitmap_fill to mark all channels as in-use up-front, and remove
  some now-redundant bitmap initialization loops.
* Only mark a channel as free once all channel-related initialization has
  completed.

Finally, the successful exit path from _init always has ret==0, so just
hard-code that return. The error path still returns ret.

Signed-off-by: default avatarStephen Warren <swarren@nvidia.com>
Signed-off-by: default avatarColin Cross <ccross@android.com>
parent ddb7d5d8

arch/arm/mach-tegra/dma.c

+10 −12
Original line number Diff line number Diff line
@@ -127,6 +127,7 @@ struct tegra_dma_channel { 


#define  NV_DMA_MAX_CHANNELS  32



static bool tegra_dma_initialized;

static DEFINE_MUTEX(tegra_dma_lock);



static DECLARE_BITMAP(channel_usage, NV_DMA_MAX_CHANNELS);
@@ -352,6 +353,9 @@ struct tegra_dma_channel *tegra_dma_allocate_channel(int mode) 
	int channel;

	struct tegra_dma_channel *ch = NULL;



	if (WARN_ON(!tegra_dma_initialized))

		return NULL;



	mutex_lock(&tegra_dma_lock);



	/* first channel is the shared channel */
@@ -678,6 +682,8 @@ int __init tegra_dma_init(void) 
	void __iomem *addr;

	struct clk *c;



	bitmap_fill(channel_usage, NV_DMA_MAX_CHANNELS);



	c = clk_get_sys("tegra-dma", NULL);

	if (IS_ERR(c)) {

		pr_err("Unable to get clock for APB DMA\n");
@@ -696,18 +702,9 @@ int __init tegra_dma_init(void) 
	writel(0xFFFFFFFFul >> (31 - TEGRA_SYSTEM_DMA_CH_MAX),

	       addr + APB_DMA_IRQ_MASK_SET);



	memset(channel_usage, 0, sizeof(channel_usage));

	memset(dma_channels, 0, sizeof(dma_channels));



	/* Reserve all the channels we are not supposed to touch */

	for (i = 0; i < TEGRA_SYSTEM_DMA_CH_MIN; i++)

		__set_bit(i, channel_usage);



	for (i = TEGRA_SYSTEM_DMA_CH_MIN; i <= TEGRA_SYSTEM_DMA_CH_MAX; i++) {

		struct tegra_dma_channel *ch = &dma_channels[i];



		__clear_bit(i, channel_usage);



		ch->id = i;

		snprintf(ch->name, TEGRA_DMA_NAME_SIZE, "dma_channel_%d", i);
@@ -726,14 +723,15 @@ int __init tegra_dma_init(void) 
			goto fail;

		}

		ch->irq = irq;



		__clear_bit(i, channel_usage);

	}

	/* mark the shared channel allocated */

	__set_bit(TEGRA_SYSTEM_DMA_CH_MIN, channel_usage);



	for (i = TEGRA_SYSTEM_DMA_CH_MAX+1; i < NV_DMA_MAX_CHANNELS; i++)

		__set_bit(i, channel_usage);

	tegra_dma_initialized = true;



	return ret;

	return 0;

fail:

	writel(0, addr + APB_DMA_GEN);

	for (i = TEGRA_SYSTEM_DMA_CH_MIN; i <= TEGRA_SYSTEM_DMA_CH_MAX; i++) {

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