Re: [PATCH 02/10] dmaengine: sun6i: Correct burst length field offsets for H3

Maxime Ripard
2017-09-04T07:59:38Z

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On Mon, Sep 04, 2017 at 12:40:53AM +0200, Stefan Brüns wrote:
> For the H3, the burst lengths field offsets in the channel configuration
> register differs from earlier SoC generations.
>
> Using the A31 register macros actually configured the H3 controller
> do to bursts of length 1 always, which although working leads to higher
> bus utilisation.
>
> Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
> ---
> drivers/dma/sun6i-dma.c | 28 +++++++++++++++++++++-------
> 1 file changed, 21 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index 1d9b3be30d22..f1a139f0102f 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -68,13 +68,15 @@
> #define DMA_CHAN_CFG_SRC_DRQ(x) ((x) & 0x1f)
> #define DMA_CHAN_CFG_SRC_IO_MODE BIT(5)
> #define DMA_CHAN_CFG_SRC_LINEAR_MODE (0 << 5)
> -#define DMA_CHAN_CFG_SRC_BURST(x) (((x) & 0x3) << 7)
> +#define DMA_CHAN_CFG_SRC_BURST_A31(x) (((x) & 0x3) << 7)
> +#define DMA_CHAN_CFG_SRC_BURST_H3(x) (((x) & 0x3) << 6)
> #define DMA_CHAN_CFG_SRC_WIDTH(x) (((x) & 0x3) << 9)
>
> #define DMA_CHAN_CFG_DST_DRQ(x) (DMA_CHAN_CFG_SRC_DRQ(x) << 16)
> #define DMA_CHAN_CFG_DST_IO_MODE (DMA_CHAN_CFG_SRC_IO_MODE << 16)
> #define DMA_CHAN_CFG_DST_LINEAR_MODE (DMA_CHAN_CFG_SRC_LINEAR_MODE << 16)
> -#define DMA_CHAN_CFG_DST_BURST(x) (DMA_CHAN_CFG_SRC_BURST(x) << 16)
> +#define DMA_CHAN_CFG_DST_BURST_A31(x) (DMA_CHAN_CFG_SRC_BURST_A31(x) << 16)
> +#define DMA_CHAN_CFG_DST_BURST_H3(x) (DMA_CHAN_CFG_SRC_BURST_H3(x) << 16)
> #define DMA_CHAN_CFG_DST_WIDTH(x) (DMA_CHAN_CFG_SRC_WIDTH(x) << 16)
>
> #define DMA_CHAN_CUR_SRC 0x10
> @@ -554,11 +556,17 @@ static int set_config(struct sun6i_dma_dev *sdev,
> if (dst_width < 0)
> return dst_width;
>
> - *p_cfg = DMA_CHAN_CFG_SRC_BURST(src_burst) |
> - DMA_CHAN_CFG_SRC_WIDTH(src_width) |
> - DMA_CHAN_CFG_DST_BURST(dst_burst) |
> + *p_cfg = DMA_CHAN_CFG_SRC_WIDTH(src_width) |
> DMA_CHAN_CFG_DST_WIDTH(dst_width);
>
> + if (sdev->cfg->dmac_variant == DMAC_VARIANT_H3) {
> + *p_cfg |= DMA_CHAN_CFG_SRC_BURST_H3(src_burst) |
> + DMA_CHAN_CFG_DST_BURST_H3(dst_burst);
> + } else {
> + *p_cfg |= DMA_CHAN_CFG_SRC_BURST_A31(src_burst) |
> + DMA_CHAN_CFG_DST_BURST_A31(dst_burst);
> + }
> +

I guess we have two options to support that properly. We could either
have a different function that would generate that register value
based on the parameters we have, or duplicate the set_config function
entirely, with function pointer stored in the configuration.

I think I prefer the former, as it reduces the code duplication.

Maxime

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

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