linux-kernel - Re: [PATCH 04/10] dmaengine: sun6i: Enable additional burst lengths/widths on H3

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Date:   Mon, 4 Sep 2017 10:00:25 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Stefan Brüns <stefan.bruens@...h-aachen.de>
Cc:     linux-sunxi@...glegroups.com, devicetree@...r.kernel.org,
        dmaengine@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Code Kipper <codekipper@...il.com>,
        Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH 04/10] dmaengine: sun6i: Enable additional burst
 lengths/widths on H3

On Mon, Sep 04, 2017 at 12:40:55AM +0200, Stefan Brüns wrote:
> The H3 supports bursts lengths of 1, 4, 8 and 16 transfers, each with
> a width of 1, 2, 4 or 8 bytes.
> 
> The register value for the the width is log2-encoded, change the
> conversion function to provide the correct value for width == 8.
> 
> Signed-off-by: Stefan Brüns <stefan.bruens@...h-aachen.de>
> ---
>  drivers/dma/sun6i-dma.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index c5644bd0f91a..335a8ec88b0b 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -263,8 +263,12 @@ static inline s8 convert_burst(u32 maxburst)
>  	switch (maxburst) {
>  	case 1:
>  		return 0;
> +	case 4:
> +		return 1;
>  	case 8:
>  		return 2;
> +	case 16:
> +		return 3;
>  	default:
>  		return -EINVAL;
>  	}
> @@ -272,7 +276,7 @@ static inline s8 convert_burst(u32 maxburst)
>  
>  static inline s8 convert_buswidth(enum dma_slave_buswidth addr_width)
>  {
> -	return addr_width >> 1;
> +	return ilog2(addr_width);
>  }
>  
>  static size_t sun6i_get_chan_size(struct sun6i_pchan *pchan)
> @@ -1152,6 +1156,12 @@ static int sun6i_dma_probe(struct platform_device *pdev)
>  						  BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
>  	sdc->src_burst_lengths			= BIT(1) | BIT(8);
>  	sdc->dst_burst_lengths			= BIT(1) | BIT(8);
> +	if (sdc->cfg->dmac_variant == DMAC_VARIANT_H3) {
> +		sdc->slave.src_addr_widths |= BIT(DMA_SLAVE_BUSWIDTH_8_BYTES);
> +		sdc->slave.dst_addr_widths |= BIT(DMA_SLAVE_BUSWIDTH_8_BYTES);
> +		sdc->src_burst_lengths     |= BIT(4) | BIT(16);
> +		sdc->dst_burst_lengths     |= BIT(4) | BIT(16);
> +	}

The rest looks good, but that should be stored in the sun6i_dma_config
structure too.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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