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SubjectRe: [PATCH] dma: pl330: ensure DMA descriptors are zero-initialised
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Hi Will,

On Fri, Nov 29, 2013 at 5:20 PM, Will Deacon <will.deacon@arm.com> wrote:
>
> I see the following splat with 3.13-rc1 when attempting to perform DMA:
>
> [ 253.004516] Alignment trap: not handling instruction e1902f9f at [<c0204b40>]
> [ 253.004583] Unhandled fault: alignment exception (0x221) at 0xdfdfdfd7
> [ 253.004646] Internal error: : 221 [#1] PREEMPT SMP ARM
> [ 253.004691] Modules linked in: dmatest(+) [last unloaded: dmatest]
> [ 253.004798] CPU: 0 PID: 671 Comm: kthreadd Not tainted 3.13.0-rc1+ #2
> [ 253.004864] task: df9b0900 ti: df03e000 task.ti: df03e000
> [ 253.004937] PC is at dmaengine_unmap_put+0x14/0x34
> [ 253.005010] LR is at pl330_tasklet+0x3c8/0x550
> [ 253.005087] pc : [<c0204b44>] lr : [<c0207478>] psr: a00e0193
> [ 253.005087] sp : df03fe48 ip : 00000000 fp : df03bf18
> [ 253.005178] r10: bf00e108 r9 : 00000001 r8 : 00000000
> [ 253.005245] r7 : df837040 r6 : dfb41800 r5 : df837048 r4 : df837000
> [ 253.005316] r3 : dfdfdfcf r2 : dfb41f80 r1 : df837048 r0 : dfdfdfd7
> [ 253.005384] Flags: NzCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel
> [ 253.005459] Control: 30c5387d Table: 9fb9ba80 DAC: fffffffd
> [ 253.005520] Process kthreadd (pid: 671, stack limit = 0xdf03e248)
>
> This is due to desc->txd.unmap containing garbage (uninitialised memory).
>
> Rather than add another dummy initialisation to _init_desc, instead
> ensure that the descriptors are zero-initialised during allocation and
> remove the dummy, per-field initialisation.
>
> Cc: Jassi Brar <jaswinder.singh@linaro.org>
> Cc: Vinod Koul <vinod.koul@intel.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
> ---
> drivers/dma/pl330.c | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index 98641eaca080..79e52a94f054 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -2492,14 +2492,8 @@ static dma_cookie_t pl330_tx_submit(struct dma_async_tx_descriptor *tx)
>
> static inline void _init_desc(struct dma_pl330_desc *desc)
> {
> - desc->pchan = NULL;
> desc->req.x = &desc->px;
> desc->req.token = desc;
> - desc->rqcfg.swap = SWAP_NO;
> - desc->rqcfg.privileged = 0;
> - desc->rqcfg.insnaccess = 0;
> - desc->rqcfg.scctl = SCCTRL0;
> - desc->rqcfg.dcctl = DCCTRL0;
>
These happen to evaluate to 0, but for completeness sake they ought to
be initialized somewhere. Otherwise we might as well drop these
members.

However I don't strongly feel about either way. So whatever comes in v2...

Acked-by: Jassi Brar <jassisinghbrar@gmail.com>


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