On 2024-02-04 6:59 am, Andrea della Porta wrote:
> From: Phil Elwell <[email protected]>
>
> Slave addresses for DMA are meant to be supplied as physical addresses
> (contrary to what struct snd_dmaengine_dai_dma_data does). It is up to
> the DMA controller driver to perform the translation based on its own
> view of the world, as described in Device Tree.
>
> Now that the Pi Device Trees have the correct peripheral mappings,
> replace the hacky address munging with phys_to_dma().
>
> Signed-off-by: Phil Elwell <[email protected]>
> ---
> drivers/dma/bcm2835-dma.c | 23 +++++------------------
> 1 file changed, 5 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index 237dcdb8d726..077812eda609 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -18,6 +18,7 @@
> * Copyright 2012 Marvell International Ltd.
> */
> #include <linux/dmaengine.h>
> +#include <linux/dma-direct.h>
Please read the comment at the top of that file; this driver is
definitely not a DMA API implementation, and should not be including it.
> #include <linux/dma-mapping.h>
> #include <linux/dmapool.h>
> #include <linux/err.h>
> @@ -980,22 +981,12 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
> if (direction == DMA_DEV_TO_MEM) {
> if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> return NULL;
> - src = c->cfg.src_addr;
> - /*
> - * One would think it ought to be possible to get the physical
> - * to dma address mapping information from the dma-ranges DT
> - * property, but I've not found a way yet that doesn't involve
> - * open-coding the whole thing.
> - */
> - if (c->is_40bit_channel)
> - src |= 0x400000000ull;
> + src = phys_to_dma(chan->device->dev, c->cfg.src_addr);
FWIW I'd argue that abusing DMA API internals like this is even more
hacky than bypassing it entirely. The appropriate public API for setting
up the device end of a transfer is dma_map_resource(). Now, it *is* the
case currently that the dma-direct implementation of that does not take
dma_range_map into account, but that's already an open question:
https://lore.kernel.org/linux-iommu/[email protected]/
Thanks,
Robin.
> info |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
> } else {
> if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> return NULL;
> - dst = c->cfg.dst_addr;
> - if (c->is_40bit_channel)
> - dst |= 0x400000000ull;
> + dst = phys_to_dma(chan->device->dev, c->cfg.dst_addr);
> info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
> }
>
> @@ -1064,17 +1055,13 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
> if (direction == DMA_DEV_TO_MEM) {
> if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> return NULL;
> - src = c->cfg.src_addr;
> - if (c->is_40bit_channel)
> - src |= 0x400000000ull;
> + src = phys_to_dma(chan->device->dev, c->cfg.src_addr);
> dst = buf_addr;
> info |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
> } else {
> if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> return NULL;
> - dst = c->cfg.dst_addr;
> - if (c->is_40bit_channel)
> - dst |= 0x400000000ull;
> + dst = phys_to_dma(chan->device->dev, c->cfg.dst_addr);
> src = buf_addr;
> info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
>