Re: [PATCH 34/39] dmaengine: ste_dma40: Convert data_width fromregister bit format to value

[Vinod Koul]

On Wed, May 15, 2013 at 10:51:57AM +0100, Lee Jones wrote:
> When a DMA client requests and configures a DMA channel, it requests
> data_width in Bytes. The DMA40 driver then swiftly converts it over to
> the necessary register bit value. Unfortunately, for any subsequent
> calculations we have to shift '1' by the bit pattern (1 << data_width)
> times to make any sense of it.
> 
> This patch flips the semantics on its head and only converts the value
> to its respective register bit pattern when writing to registers. This
> way we can use the true data_width (in Bytes) value.
> 
> Cc: Vinod Koul <vinod.koul@xxxxxxxxx>
> Cc: Dan Williams <djbw@xxxxxx>
> Cc: Per Forlin <per.forlin@xxxxxxxxxxxxxx>
> Cc: Rabin Vincent <rabin@xxxxxx>
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
  
> @@ -2804,14 +2781,24 @@ static int d40_set_runtime_config(struct dma_chan *chan,
>  		src_maxburst = dst_maxburst * dst_addr_width / src_addr_width;
>  	}
>  
> +	/* Only valid widths are; 1, 2, 4 and 8. */
> +	if (src_addr_width <= DMA_SLAVE_BUSWIDTH_UNDEFINED ||
> +	    src_addr_width >  DMA_SLAVE_BUSWIDTH_8_BYTES   ||
> +	    dst_addr_width <= DMA_SLAVE_BUSWIDTH_UNDEFINED ||
> +	    dst_addr_width >  DMA_SLAVE_BUSWIDTH_8_BYTES   ||
> +	    ((src_addr_width > 1) && (src_addr_width & 1)) ||
> +	    ((dst_addr_width > 1) && (dst_addr_width & 1)))
> +		return -EINVAL;
how about a simple macro to check above..

> +
> +	cfg->src_info.data_width = src_addr_width;
> +	cfg->dst_info.data_width = dst_addr_width;
> +
>  	ret = dma40_config_to_halfchannel(d40c, &cfg->src_info,
> -					  src_addr_width,
>  					  src_maxburst);
>  	if (ret)
>  		return ret;
>  
>  	ret = dma40_config_to_halfchannel(d40c, &cfg->dst_info,
> -					  dst_addr_width,
>  					  dst_maxburst);
>  	if (ret)
>  		return ret;
> diff --git a/drivers/dma/ste_dma40_ll.c b/drivers/dma/ste_dma40_ll.c
> index 5ddd724..a035dfe 100644
> --- a/drivers/dma/ste_dma40_ll.c
> +++ b/drivers/dma/ste_dma40_ll.c
> @@ -10,6 +10,18 @@
>  
>  #include "ste_dma40_ll.h"
>  
> +u8 d40_width_to_bits(enum dma_slave_buswidth width)
> +{
> +	if (width == DMA_SLAVE_BUSWIDTH_1_BYTE)
> +		return STEDMA40_ESIZE_8_BIT;
> +	else if (width == DMA_SLAVE_BUSWIDTH_2_BYTES)
> +		return STEDMA40_ESIZE_16_BIT;
> +	else if (width == DMA_SLAVE_BUSWIDTH_8_BYTES)
> +		return STEDMA40_ESIZE_64_BIT;
> +	else
> +		return STEDMA40_ESIZE_32_BIT;
> +}
> +
Switch looks better for this and how about
	return fls(width);

as your defines are 0...3 and dmaengine define 1,2,..8 for same thing
then you can also get rid of STEDMA40_XXX_WIDTH macros!


> @@ -70,13 +70,6 @@ enum stedma40_flow_ctrl {
>  	STEDMA40_FLOW_CTRL,
>  };
>  
> -enum stedma40_periph_data_width {
> -	STEDMA40_BYTE_WIDTH = STEDMA40_ESIZE_8_BIT,
> -	STEDMA40_HALFWORD_WIDTH = STEDMA40_ESIZE_16_BIT,
> -	STEDMA40_WORD_WIDTH = STEDMA40_ESIZE_32_BIT,
> -	STEDMA40_DOUBLEWORD_WIDTH = STEDMA40_ESIZE_64_BIT
> -};
nice

--
~Vinod
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