linux-kernel - Re: [PATCH v2 2/2] DW DMAC: add multi-block property to device tree

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Message-ID: <1479491012.22212.35.camel@linux.intel.com>
Date:   Fri, 18 Nov 2016 19:43:32 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        devicetree@...r.kernel.org
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        linux-kernel@...r.kernel.org, vinod.koul@...el.com,
        dmaengine@...r.kernel.org, linux-snps-arc@...ts.infradead.org
Subject: Re: [PATCH v2 2/2] DW DMAC: add multi-block property to device tree

On Fri, 2016-11-18 at 19:53 +0300, Eugeniy Paltsev wrote:
> Several versions of DW DMAC have multi block transfers hardware
> support. Hardware support of multi block transfers is disabled
> by default if we use DT to configure DMAC and software emulation
> of multi block transfers used instead.
> Add multi-block property, so it is possible to enable hardware
> multi block transfers (if present) via DT.
> 
> Switch from per device is_nollp variable to multi_block array
> to be able enable/disable multi block transfers separately per
> channel.
> 
> Update DT documentation.
> 
> Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> ---
>  Documentation/devicetree/bindings/dma/snps-dma.txt | 2 ++
>  drivers/dma/dw/core.c                              | 2 +-
>  drivers/dma/dw/platform.c                          | 5 +++++
>  include/linux/platform_data/dma-dw.h               | 4 ++--
>  4 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/dma/snps-dma.txt
> b/Documentation/devicetree/bindings/dma/snps-dma.txt
> index 0f55832..03d6d6d 100644
> --- a/Documentation/devicetree/bindings/dma/snps-dma.txt
> +++ b/Documentation/devicetree/bindings/dma/snps-dma.txt
> @@ -27,6 +27,8 @@ Optional properties:
>    that services interrupts for this device
>  - is_private: The device channels should be marked as private and not
> for by the
>    general purpose DMA channel allocator. False if not passed.
> +- multi-block: Multi block transfers supported by hardware per AHB
> master.
> +  0 (default): not supported, 1: supported.

Since default is "not supported" you have to update users accordingly.
(Check platform data and existing DTS).
 
>  Example:
>  
> diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
> index c2c0a61..f2a3d06 100644
> --- a/drivers/dma/dw/core.c
> +++ b/drivers/dma/dw/core.c
> @@ -1569,7 +1569,7 @@ int dw_dma_probe(struct dw_dma_chip *chip)
>  				(dwc_params >> DWC_PARAMS_MBLK_EN &
> 0x1) == 0;
>  		} else {
>  			dwc->block_size = pdata->block_size;

> -			dwc->nollp = pdata->is_nollp;
> +			dwc->nollp = pdata->multi_block[i];

This inverts the default logic.

>  		}
>  	}
>  
> diff --git a/drivers/dma/dw/platform.c b/drivers/dma/dw/platform.c
> index aa7a5c1..b262fd3 100644
> --- a/drivers/dma/dw/platform.c
> +++ b/drivers/dma/dw/platform.c
> @@ -152,6 +152,11 @@ dw_dma_parse_dt(struct platform_device *pdev)
>  			pdata->data_width[tmp] = BIT(arr[tmp] &
> 0x07);
>  	}
>  
> +	if (!of_property_read_u32_array(np, "multi-block", arr,
> nr_masters)) {
> +		for (tmp = 0; tmp < nr_masters; tmp++)
> +			pdata->multi_block[tmp] = arr[tmp];
> +	}
> +
>  	return pdata;
>  }
>  #else
> diff --git a/include/linux/platform_data/dma-dw.h
> b/include/linux/platform_data/dma-dw.h
> index 5f0e11e..0773bb4 100644
> --- a/include/linux/platform_data/dma-dw.h
> +++ b/include/linux/platform_data/dma-dw.h
> @@ -40,19 +40,18 @@ struct dw_dma_slave {
>   * @is_private: The device channels should be marked as private and
> not for
>   *	by the general purpose DMA channel allocator.
>   * @is_memcpy: The device channels do support memory-to-memory
> transfers.
> - * @is_nollp: The device channels does not support multi block
> transfers.
>   * @chan_allocation_order: Allocate channels starting from 0 or 7
>   * @chan_priority: Set channel priority increasing from 0 to 7 or 7
> to 0.
>   * @block_size: Maximum block size supported by the controller
>   * @nr_masters: Number of AHB masters supported by the controller
>   * @data_width: Maximum data width supported by hardware per AHB
> master
>   *		(in bytes, power of 2)
> + * @multi_block: Multi block transfers supported by hardware per AHB
> master.
>   */
>  struct dw_dma_platform_data {
>  	unsigned int	nr_channels;
>  	bool		is_private;
>  	bool		is_memcpy;
> -	bool		is_nollp;
>  #define CHAN_ALLOCATION_ASCENDING	0	/* zero to seven */
>  #define CHAN_ALLOCATION_DESCENDING	1	/* seven to zero
> */
>  	unsigned char	chan_allocation_order;
> @@ -62,6 +61,7 @@ struct dw_dma_platform_data {
>  	unsigned int	block_size;
>  	unsigned char	nr_masters;
>  	unsigned char	data_width[DW_DMA_MAX_NR_MASTERS];
> +	unsigned char	multi_block[DW_DMA_MAX_NR_MASTERS];
>  };
>  
>  #endif /* _PLATFORM_DATA_DMA_DW_H */

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy