Re: [PATCH 04/18] dmaengine: bcm2835: move CB info generation into separate function

Frank Li
2024-06-05T16:05:16Z

On Fri, May 24, 2024 at 07:26:48PM +0100, Dave Stevenson wrote:
> From: Stefan Wahren <stefan.wahren@i2se.com>
>
> Actually the generation of the Control Block info follows some simple
> rules. So handle this with a separate function to avoid open coding
> for every DMA operation. Another advantage is that we can easier
> introduce other platforms with different info bits.

May simple said as:

Introduce common help funtion to prepare Control Block Info to avoid
dupicate code in every DMA operation.

>
> Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
> ---
> drivers/dma/bcm2835-dma.c | 50 +++++++++++++++++++++++++--------------
> 1 file changed, 32 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index 528c4593b45a..7cef7ff89575 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -201,6 +201,34 @@ static inline struct bcm2835_desc *to_bcm2835_dma_desc(
> return container_of(t, struct bcm2835_desc, vd.tx);
> }
>
> +static u32 bcm2835_dma_prepare_cb_info(struct bcm2835_chan *c,
> + enum dma_transfer_direction direction,
> + bool zero_page)
> +{
> + u32 result;
> +
> + if (direction == DMA_MEM_TO_MEM)
> + return BCM2835_DMA_D_INC | BCM2835_DMA_S_INC;
> +
> + result = BCM2835_DMA_WAIT_RESP;
> +
> + /* Setup DREQ channel */
> + if (c->dreq != 0)
> + result |= BCM2835_DMA_PER_MAP(c->dreq);
> +
> + if (direction == DMA_DEV_TO_MEM) {
> + result |= BCM2835_DMA_S_DREQ | BCM2835_DMA_D_INC;
> + } else {
> + result |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
> +
> + /* non-lite channels can write zeroes w/o accessing memory */
> + if (zero_page && !c->is_lite_channel)
> + result |= BCM2835_DMA_S_IGNORE;
> + }
> +
> + return result;
> +}
> +
> static void bcm2835_dma_free_cb_chain(struct bcm2835_desc *desc)
> {
> size_t i;
> @@ -615,7 +643,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_memcpy(
> {
> struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
> struct bcm2835_desc *d;
> - u32 info = BCM2835_DMA_D_INC | BCM2835_DMA_S_INC;
> + u32 info = bcm2835_dma_prepare_cb_info(c, DMA_MEM_TO_MEM, false);
> u32 extra = BCM2835_DMA_INT_EN | BCM2835_DMA_WAIT_RESP;
> size_t max_len = bcm2835_dma_max_frame_length(c);
> size_t frames;
> @@ -646,7 +674,7 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
> struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
> struct bcm2835_desc *d;
> dma_addr_t src = 0, dst = 0;
> - u32 info = BCM2835_DMA_WAIT_RESP;
> + u32 info = bcm2835_dma_prepare_cb_info(c, direction, false);
> u32 extra = BCM2835_DMA_INT_EN;
> size_t frames;
>
> @@ -656,19 +684,14 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_slave_sg(
> return NULL;
> }
>
> - if (c->dreq != 0)
> - info |= BCM2835_DMA_PER_MAP(c->dreq);
> -
> if (direction == DMA_DEV_TO_MEM) {
> if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> return NULL;
> src = c->cfg.src_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;
> - info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
> }
>
> /* count frames in sg list */
> @@ -698,7 +721,8 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
> struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
> struct bcm2835_desc *d;
> dma_addr_t src, dst;
> - u32 info = BCM2835_DMA_WAIT_RESP;
> + u32 info = bcm2835_dma_prepare_cb_info(c, direction,
> + buf_addr == od->zero_page);
> u32 extra = 0;
> size_t max_len = bcm2835_dma_max_frame_length(c);
> size_t frames;
> @@ -729,26 +753,16 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
> "%s: buffer_length (%zd) is not a multiple of period_len (%zd)\n",
> __func__, buf_len, period_len);
>
> - /* Setup DREQ channel */
> - if (c->dreq != 0)
> - info |= BCM2835_DMA_PER_MAP(c->dreq);
> -
> if (direction == DMA_DEV_TO_MEM) {
> if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> return NULL;
> src = 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;
> src = buf_addr;
> - info |= BCM2835_DMA_D_DREQ | BCM2835_DMA_S_INC;
> -
> - /* non-lite channels can write zeroes w/o accessing memory */
> - if (buf_addr == od->zero_page && !c->is_lite_channel)
> - info |= BCM2835_DMA_S_IGNORE;
> }
>
> /* calculate number of frames */
> --
> 2.34.1
>