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dmaengine: bcm2835: Enforce control block alignment

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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 <[email protected]>
Cc: Frank Pavlic <[email protected]>
Cc: Martin Sperl <[email protected]>
Cc: Florian Meier <[email protected]>
Tested-by: Stefan Wahren <[email protected]>
Acked-by: Florian Kauer <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>
This commit is contained in:
Lukas Wunner 2019-01-23 09:26:00 +01:00 • committed by Vinod Koul
commit 603fe86be1
1 changed files with 5 additions and 1 deletions
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6
drivers/dma/bcm2835-dma.c
View file

@ -503,8 +503,12 @@ 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;