linux-kernel - Re: [PATCH v2 2/3] dmaengine: qcom: bam_dma: wrapper functions for command descriptor

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Date:   Wed, 19 Jul 2017 15:39:02 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Abhishek Sahu <absahu@...eaurora.org>
Cc:     andy.gross@...aro.org, david.brown@...aro.org,
        dan.j.williams@...el.com, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] dmaengine: qcom: bam_dma: wrapper functions for
 command descriptor

On Mon, Jun 26, 2017 at 06:19:28PM +0530, Abhishek Sahu wrote:
> QCOM BAM also supports command descriptor which allows the SW to
> create descriptors of type command which does not generate any
> data transmissions but configures registers in the peripheral.
> In command descriptor the 32bit address point to the start of
> the command block which holds the command elements and the
> 16bit size define the size of the command block.
> 
> Each Command Element is structured by 4 words:
>     Write command: address + cmd
>                    register data
>                    register mask
>                    reserved
> 
>     Read command: address + cmd
>                   read data result address,
>                   reserved
>                   reserved
> 
> This patch creates a new header file for BAM driver which contains the
> structures and wrapper functions for command descriptor. This file will
> be used by different QCOM peripheral drivers for forming the command
> descriptor
> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>  include/linux/dma/qcom_bam_dma.h | 79 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 79 insertions(+)
>  create mode 100644 include/linux/dma/qcom_bam_dma.h
> 
> diff --git a/include/linux/dma/qcom_bam_dma.h b/include/linux/dma/qcom_bam_dma.h
> new file mode 100644
> index 0000000..077d43a
> --- /dev/null
> +++ b/include/linux/dma/qcom_bam_dma.h
> @@ -0,0 +1,79 @@
> +/*
> + * Copyright (c) 2016-2017, The Linux Foundation. All rights reserved.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#ifndef _QCOM_BAM_DMA_H
> +#define _QCOM_BAM_DMA_H
> +
> +#include <asm/byteorder.h>
> +
> +/*
> + * This data type corresponds to the native Command Element
> + * supported by BAM DMA Engine.
> + *
> + * @cmd_and_addr - upper 8 bits command and lower 24 bits register address.
> + * @data - for write command: content to be written into peripheral register.
> + *	   for read command: dest addr to write peripheral register value.
> + * @mask - register mask.
> + * @reserved - for future usage.
> + *
> + */
> +struct bam_cmd_element {
> +	__le32 cmd_and_addr;
> +	__le32 data;
> +	__le32 mask;
> +	__le32 reserved;
> +};
> +
> +/*
> + * This enum indicates the command type in a command element
> + */
> +enum bam_command_type {
> +	BAM_WRITE_COMMAND = 0,
> +	BAM_READ_COMMAND,
> +};
> +
> +/*
> + * prep_bam_ce_le32 - Wrapper function to prepare a single BAM command
> + * element with the data already in le32 format.
> + *
> + * @bam_ce: bam command element
> + * @addr: target address
> + * @cmd: BAM command
> + * @data: actual data for write and dest addr for read in le32
> + */
> +static inline void
> +bam_prep_ce_le32(struct bam_cmd_element *bam_ce, u32 addr,
> +		 enum bam_command_type cmd, __le32 data)
> +{
> +	bam_ce->cmd_and_addr =
> +		cpu_to_le32((addr & 0xffffff) | ((cmd & 0xff) << 24));
> +	bam_ce->data = data;
> +	bam_ce->mask = cpu_to_le32(0xffffffff);
> +}

Is this being used by clients?

> +
> +/*
> + * bam_prep_ce - Wrapper function to prepare a single BAM command element
> + * with the data.
> + *
> + * @bam_ce: BAM command element
> + * @addr: target address
> + * @cmd: BAM command
> + * @data: actual data for write and dest addr for read
> + */
> +static inline void
> +bam_prep_ce(struct bam_cmd_element *bam_ce, u32 addr,
> +	    enum bam_command_type cmd, u32 data)
> +{
> +	bam_prep_ce_le32(bam_ce, addr, cmd, cpu_to_le32(data));
> +}
> +#endif
> -- 
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
> 

-- 
~Vinod