[arm/tegra] dma: Dma allocation should be thread safe

The dma can be allocated from multiple client in run time
and so it should be thread/smp safe.

Returning proper error pointer in case of there is no dma to
allocate.

bug 723220

Change-Id: Ifb333d4b14e32be561e34a0d7668a2d631ac80c6
(cherry picked from commit db2d10f715fcdd6fdaf5fc7ea8e27a505f8332da)
Reviewed-on: http://git-master/r/5769
Reviewed-by: Laxman Dewangan <ldewangan@nvidia.com>
Tested-by: Laxman Dewangan <ldewangan@nvidia.com>
Reviewed-by: Bharat Nihalani <bnihalani@nvidia.com>

2 files changed, 18 insertions, 5 deletions

diff --git a/arch/arm/mach-tegra/dma.c b/arch/arm/mach-tegra/dma.c
index 7eb0bb758b67..ad9f3a05a68b 100644
--- a/arch/arm/mach-tegra/dma.c
+++ b/arch/arm/mach-tegra/dma.c
@@ -132,6 +132,8 @@ struct tegra_dma_channel {
 
 #define  NV_DMA_MAX_CHANNELS  32
 
+static DEFINE_SPINLOCK(global_dma_lock);
+
 static DECLARE_BITMAP(channel_usage, NV_DMA_MAX_CHANNELS);
 static struct tegra_dma_channel dma_channels[NV_DMA_MAX_CHANNELS];
 
@@ -471,6 +473,9 @@ struct tegra_dma_channel *tegra_dma_allocate_channel(int mode)
 {
 	int channel;
 	struct tegra_dma_channel *ch;
+	unsigned long irq_flags;
+
+	spin_lock_irqsave(&global_dma_lock, irq_flags);
 
 	/* first channel is the shared channel */
 	if (mode & TEGRA_DMA_SHARED) {
@@ -478,10 +483,14 @@ struct tegra_dma_channel *tegra_dma_allocate_channel(int mode)
 	} else {
 		channel = find_first_zero_bit(channel_usage,
 			ARRAY_SIZE(dma_channels));
-		if (channel >= ARRAY_SIZE(dma_channels))
-			return ERR_PTR(ENODEV);
+		if (channel >= ARRAY_SIZE(dma_channels)) {
+			spin_unlock_irqrestore(&global_dma_lock, irq_flags);
+			return ERR_PTR(-ENODEV);
+		}
 	}
 	__set_bit(channel, channel_usage);
+	spin_unlock_irqrestore(&global_dma_lock, irq_flags);
+
 	ch = &dma_channels[channel];
 	ch->mode = mode;
 	return ch;
@@ -490,10 +499,14 @@ EXPORT_SYMBOL(tegra_dma_allocate_channel);
 
 void tegra_dma_free_channel(struct tegra_dma_channel *ch)
 {
+	unsigned long irq_flags;
 	if (ch->mode & TEGRA_DMA_SHARED)
 		return;
 	tegra_dma_cancel(ch);
+	spin_lock_irqsave(&global_dma_lock, irq_flags);
 	__clear_bit(ch->id, channel_usage);
+	spin_unlock_irqrestore(&global_dma_lock, irq_flags);
+
 }
 EXPORT_SYMBOL(tegra_dma_free_channel);
 
diff --git a/arch/arm/mach-tegra/nvrm/io/ap15/rm_spi_slink.c b/arch/arm/mach-tegra/nvrm/io/ap15/rm_spi_slink.c
index cf7fd9493820..26ee1e1a6457 100644
--- a/arch/arm/mach-tegra/nvrm/io/ap15/rm_spi_slink.c
+++ b/arch/arm/mach-tegra/nvrm/io/ap15/rm_spi_slink.c
@@ -57,7 +57,7 @@
 
 #include "linux/module.h"
 #include "mach/dma.h"
-
+#include "linux/err.h"
 
 // Combined maximum spi/slink controllers
 #define MAX_SPI_SLINK_INSTANCE (MAX_SLINK_CONTROLLERS + MAX_SPI_CONTROLLERS)
@@ -513,10 +513,10 @@ static NvError AllocateDmas(NvRmSpiHandle hRmSpiSlink)
     hRmSpiSlink->hTxDma = NULL;
 
     hRmSpiSlink->hRxDma = tegra_dma_allocate_channel(TEGRA_DMA_MODE_ONESHOT);
-    if (hRmSpiSlink->hRxDma)
+    if (!IS_ERR_OR_NULL(hRmSpiSlink->hRxDma))
     {
         hRmSpiSlink->hTxDma = tegra_dma_allocate_channel(TEGRA_DMA_MODE_ONESHOT);
-        if (!hRmSpiSlink->hTxDma)
+        if (IS_ERR_OR_NULL(hRmSpiSlink->hTxDma))
         {
             tegra_dma_free_channel(hRmSpiSlink->hRxDma);
             hRmSpiSlink->hRxDma = NULL;