linux-kernel - Re: [PATCH 07/12] bcm2835-dma: Support dma flags for multi-beat burst

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Message-ID: <ZcM9slv_x-CltW6y@matsya>
Date: Wed, 7 Feb 2024 09:22:10 +0100
From: Vinod Koul <vkoul@...nel.org>
To: Andrea della Porta <andrea.porta@...e.com>
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	dmaengine@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Maxime Ripard <maxime@...no.tech>,
	Dom Cobley <popcornmix@...il.com>,
	Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH 07/12] bcm2835-dma: Support dma flags for multi-beat burst

On 04-02-24, 07:59, Andrea della Porta wrote:
> From: Dom Cobley <popcornmix@...il.com>
> 
> Add a control bit to enable a multi-beat burst on a DMA.
> This improves DMA performance and is required for HDMI audio.
> 
> Signed-off-by: Dom Cobley <popcornmix@...il.com>
> Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
> ---
>  drivers/dma/bcm2835-dma.c | 28 ++++++++++++++++++++--------
>  1 file changed, 20 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index d8d1f9ba2572..a20700a400a2 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -156,7 +156,8 @@ struct bcm2835_desc {
>  #define BCM2835_DMA_S_WIDTH	BIT(9) /* 128bit writes if set */
>  #define BCM2835_DMA_S_DREQ	BIT(10) /* enable SREQ for source */
>  #define BCM2835_DMA_S_IGNORE	BIT(11) /* ignore source reads - read 0 */
> -#define BCM2835_DMA_BURST_LENGTH(x) ((x & 15) << 12)
> +#define BCM2835_DMA_BURST_LENGTH(x) (((x) & 15) << 12)

why this changes, sounds like it does not belong here.. 


> +#define BCM2835_DMA_GET_BURST_LENGTH(x) (((x) >> 12) & 15)
>  #define BCM2835_DMA_CS_FLAGS(x) ((x) & (BCM2835_DMA_PRIORITY(15) | \
>  				      BCM2835_DMA_PANIC_PRIORITY(15) | \
>  				      BCM2835_DMA_WAIT_FOR_WRITES | \
> @@ -180,6 +181,11 @@ struct bcm2835_desc {
>  #define WIDE_DEST(x) (((x) & BCM2835_DMA_WIDE_DEST) ? \
>  		      BCM2835_DMA_D_WIDTH : 0)
>  
> +/* A fake bit to request that the driver requires multi-beat burst */
> +#define BCM2835_DMA_BURST BIT(30)
> +#define BURST_LENGTH(x) (((x) & BCM2835_DMA_BURST) ? \
> +			 BCM2835_DMA_BURST_LENGTH(3) : 0)
> +
>  /* debug register bits */
>  #define BCM2835_DMA_DEBUG_LAST_NOT_SET_ERR	BIT(0)
>  #define BCM2835_DMA_DEBUG_FIFO_ERR		BIT(1)
> @@ -282,7 +288,7 @@ struct bcm2835_desc {
>  /* the max dma length for different channels */
>  #define MAX_DMA40_LEN SZ_1G
>  
> -#define BCM2711_DMA40_BURST_LEN(x)	((min(x, 16) - 1) << 8)
> +#define BCM2711_DMA40_BURST_LEN(x)	(((x) & 15) << 8)
>  #define BCM2711_DMA40_INC		BIT(12)
>  #define BCM2711_DMA40_SIZE_32		(0 << 13)
>  #define BCM2711_DMA40_SIZE_64		(1 << 13)
> @@ -359,12 +365,16 @@ static inline uint32_t to_bcm2711_ti(uint32_t info)
>  
>  static inline uint32_t to_bcm2711_srci(uint32_t info)
>  {
> -	return ((info & BCM2835_DMA_S_INC) ? BCM2711_DMA40_INC : 0);
> +	return ((info & BCM2835_DMA_S_INC) ? BCM2711_DMA40_INC : 0) |
> +	       ((info & BCM2835_DMA_S_WIDTH) ? BCM2711_DMA40_SIZE_128 : 0) |
> +	       BCM2711_DMA40_BURST_LEN(BCM2835_DMA_GET_BURST_LENGTH(info));
>  }
>  
>  static inline uint32_t to_bcm2711_dsti(uint32_t info)
>  {
> -	return ((info & BCM2835_DMA_D_INC) ? BCM2711_DMA40_INC : 0);
> +	return ((info & BCM2835_DMA_D_INC) ? BCM2711_DMA40_INC : 0) |
> +	       ((info & BCM2835_DMA_D_WIDTH) ? BCM2711_DMA40_SIZE_128 : 0) |
> +	       BCM2711_DMA40_BURST_LEN(BCM2835_DMA_GET_BURST_LENGTH(info));
>  }
>  
>  static inline uint32_t to_bcm2711_cbaddr(dma_addr_t addr)
> @@ -933,7 +943,8 @@ 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 |
> -		   WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) | WIDE_DEST(c->dreq);
> +		   WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) |
> +		   WIDE_DEST(c->dreq) | BURST_LENGTH(c->dreq);
>  	u32 extra = BCM2835_DMA_INT_EN;
>  	size_t max_len = bcm2835_dma_max_frame_length(c);
>  	size_t frames;
> @@ -964,8 +975,8 @@ 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 = WAIT_RESP(c->dreq) |
> -		   WIDE_SOURCE(c->dreq) | WIDE_DEST(c->dreq);
> +	u32 info = WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) |
> +		   WIDE_DEST(c->dreq) | BURST_LENGTH(c->dreq);
>  	u32 extra = BCM2835_DMA_INT_EN;
>  	size_t frames;
>  
> @@ -1017,7 +1028,8 @@ 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 = WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) | WIDE_DEST(c->dreq);
> +	u32 info = WAIT_RESP(c->dreq) | WIDE_SOURCE(c->dreq) |
> +		   WIDE_DEST(c->dreq) | BURST_LENGTH(c->dreq);
>  	u32 extra = 0;
>  	size_t max_len = bcm2835_dma_max_frame_length(c);
>  	size_t frames;
> -- 
> 2.41.0

-- 
~Vinod