Per section 4.2.1.1 of the BCM2835 ARM Peripherals spec, control blocks "must start at a 256 bit aligned address": https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf This rule is currently satisfied only by accident because struct bcm2835_dma_cb has a size of 256 bit and the DMA pool API happens to allocate blocks consecutively. It seems safer to be explicit and tell the DMA pool allocator about the required alignment. Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> Cc: Frank Pavlic <f.pavlic@xxxxxxxxx> Cc: Martin Sperl <kernel@xxxxxxxxxxxxxxxx> Cc: Florian Meier <florian.meier@xxxxxxxx> --- drivers/dma/bcm2835-dma.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c index a3ecb7fd4fc2..e424e232a3d0 100644 --- a/drivers/dma/bcm2835-dma.c +++ b/drivers/dma/bcm2835-dma.c @@ -498,8 +498,12 @@ static int bcm2835_dma_alloc_chan_resources(struct dma_chan *chan) dev_dbg(dev, "Allocating DMA channel %d\n", c->ch); + /* + * Control blocks are 256 bit in length and must start at a 256 bit + * (32 byte) aligned address (BCM2835 ARM Peripherals, sec. 4.2.1.1). + */ c->cb_pool = dma_pool_create(dev_name(dev), dev, - sizeof(struct bcm2835_dma_cb), 0, 0); + sizeof(struct bcm2835_dma_cb), 32, 0); if (!c->cb_pool) { dev_err(dev, "unable to allocate descriptor pool\n"); return -ENOMEM; -- 2.19.2
