[PATCH v2] arm: davinci: fix edma dmaengine induced null pointer dereference on da830

[Tomas Novotny]

On Tue,  5 Mar 2013 10:58:22 -0500
Matt Porter <mporter at ti.com> wrote:

> This adds additional error checking to the private edma api implementation
> to catch the case where the edma_alloc_slot() has an invalid controller
> parameter. The edma dmaengine wrapper driver relies on this condition
> being handled in order to avoid setting up a second edma dmaengine
> instance on DA830.
> 
> Verfied using a DA850 with the second EDMA controller platform instance
> removed to simulate a DA830 which only has a single EDMA controller.
> 
> Reported-by: Tomas Novotny <tomas at novotny.cz>
> Signed-off-by: Matt Porter <mporter at ti.com>
> Cc: stable at vger.kernel.org # v3.7.x+
> ---
> v2: Move error check out of conditional to catch all cases
> 
>  arch/arm/mach-davinci/dma.c |    3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm/mach-davinci/dma.c b/arch/arm/mach-davinci/dma.c
> index a685e97..45b7c71 100644
> --- a/arch/arm/mach-davinci/dma.c
> +++ b/arch/arm/mach-davinci/dma.c
> @@ -743,6 +743,9 @@ EXPORT_SYMBOL(edma_free_channel);
>   */
>  int edma_alloc_slot(unsigned ctlr, int slot)
>  {
> +	if (!edma_cc[ctlr])
> +		return -EINVAL;
> +
>  	if (slot >= 0)
>  		slot = EDMA_CHAN_SLOT(slot);
>  

On the TI AM1707 based custom board:

Tested-by: Tomas Novotny <tomas at novotny.cz>