linux-kernel - Re: [PATCH 09/18] dmaengine: bcm2835: Add function to handle DMA mapping

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Date: Wed, 5 Jun 2024 14:13:26 -0400
From: Frank Li <Frank.li@....com>
To: Dave Stevenson <dave.stevenson@...pberrypi.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>,
	Vinod Koul <vkoul@...nel.org>, Maxime Ripard <mripard@...nel.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Mark Brown <broonie@...nel.org>, Christoph Hellwig <hch@....de>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Robin Murphy <robin.murphy@....com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
	Vladimir Murzin <vladimir.murzin@....com>,
	Phil Elwell <phil@...pberrypi.com>,
	Stefan Wahren <wahrenst@....net>,
	Serge Semin <Sergey.Semin@...kalelectronics.ru>,
	devicetree@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-mmc@...r.kernel.org, linux-spi@...r.kernel.org,
	iommu@...ts.linux.dev, linux-sound@...r.kernel.org
Subject: Re: [PATCH 09/18] dmaengine: bcm2835: Add function to handle DMA
 mapping

On Fri, May 24, 2024 at 07:26:53PM +0100, Dave Stevenson wrote:
> The code handling DMA mapping is currently incorrect and
> needs a sequence of fixups.

Can you descript what incorrect here? 

> Move the mapping out into a separate function and structure
> to allow for those fixes to be applied more cleanly.
> 
> Signed-off-by: Dave Stevenson <dave.stevenson@...pberrypi.com>
> ---
>  drivers/dma/bcm2835-dma.c | 46 ++++++++++++++++++++++++++++++++-------
>  1 file changed, 38 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index aefaa1f01d7f..ef1d95bae84e 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -65,6 +65,10 @@ struct bcm2835_cb_entry {
>  	dma_addr_t paddr;
>  };
>  
> +struct bcm2835_dma_chan_map {
> +	dma_addr_t addr;
> +};
> +
>  struct bcm2835_chan {
>  	struct virt_dma_chan vc;
>  
> @@ -74,6 +78,7 @@ struct bcm2835_chan {
>  	int ch;
>  	struct bcm2835_desc *desc;
>  	struct dma_pool *cb_pool;
> +	struct bcm2835_dma_chan_map map;

I suppose map should in bcm2835_desc.  if put in chan, how about client
driver create two desc by bcm2835_dma_prep_slave_sg()?

prep_slave_sg()
submit()
prep_savle_sg()
submit()
issue_pending()

Frank

>  
>  	void __iomem *chan_base;
>  	int irq_number;
> @@ -268,6 +273,19 @@ static inline bool need_dst_incr(enum dma_transfer_direction direction)
>  	}
>  
>  	return false;
> +};
> +
> +static int bcm2835_dma_map_slave_addr(struct dma_chan *chan,
> +				      phys_addr_t dev_addr,
> +				      size_t dev_size,
> +				      enum dma_data_direction dev_dir)
> +{
> +	struct bcm2835_chan *c = to_bcm2835_dma_chan(chan);
> +	struct bcm2835_dma_chan_map *map = &c->map;
> +
> +	map->addr = dev_addr;
> +
> +	return 0;
>  }
>  
>  static void bcm2835_dma_free_cb_chain(struct bcm2835_desc *desc)
> @@ -734,13 +752,19 @@ 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)
> +		if (bcm2835_dma_map_slave_addr(chan, c->cfg.src_addr,
> +					       c->cfg.src_addr_width,
> +					       DMA_TO_DEVICE))
>  			return NULL;
> -		src = c->cfg.src_addr;
> +
> +		src = c->map.addr;
>  	} else {
> -		if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> +		if (bcm2835_dma_map_slave_addr(chan, c->cfg.dst_addr,
> +					       c->cfg.dst_addr_width,
> +					       DMA_FROM_DEVICE))
>  			return NULL;
> -		dst = c->cfg.dst_addr;
> +
> +		dst = c->map.addr;
>  	}
>  
>  	/* count frames in sg list */
> @@ -795,14 +819,20 @@ static struct dma_async_tx_descriptor *bcm2835_dma_prep_dma_cyclic(
>  			      __func__, buf_len, period_len);
>  
>  	if (direction == DMA_DEV_TO_MEM) {
> -		if (c->cfg.src_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> +		if (bcm2835_dma_map_slave_addr(chan, c->cfg.src_addr,
> +					       c->cfg.src_addr_width,
> +					       DMA_TO_DEVICE))
>  			return NULL;
> -		src = c->cfg.src_addr;
> +
> +		src = c->map.addr;
>  		dst = buf_addr;
>  	} else {
> -		if (c->cfg.dst_addr_width != DMA_SLAVE_BUSWIDTH_4_BYTES)
> +		if (bcm2835_dma_map_slave_addr(chan, c->cfg.dst_addr,
> +					       c->cfg.dst_addr_width,
> +					       DMA_FROM_DEVICE))
>  			return NULL;
> -		dst = c->cfg.dst_addr;
> +
> +		dst = c->map.addr;
>  		src = buf_addr;
>  	}
>  
> -- 
> 2.34.1
>