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

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Message-ID: <5104dc704a21684ca2dbb2702f49600f@codeaurora.org>
Date:   Wed, 19 Jul 2017 17:01:08 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Vinod Koul <vinod.koul@...el.com>
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 2017-07-19 15:39, Vinod Koul wrote:
> 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?
> 

  Yes Vinod. This wrapper function will be called by clients.
  NAND driver will call this function for reading/writing
  registers from BAM DMA.

  Following is the NAND client driver patch
  http://www.spinics.net/lists/devicetree/msg183713.html

>> +
>> +/*
>> + * 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
>> 

-- 
Abhishek Sahu