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Date: Wed, 5 Jun 2024 12:05:01 -0400
From: Frank Li <Frank.li@nxp.com>
To: Dave Stevenson <dave.stevenson@raspberrypi.com>
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	Stefan Wahren <stefan.wahren@i2se.com>
Subject: Re: [PATCH 04/18] dmaengine: bcm2835: move CB info generation into
 separate function
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References: <20240524182702.1317935-1-dave.stevenson@raspberrypi.com>
 <20240524182702.1317935-5-dave.stevenson@raspberrypi.com>
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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
>