linux-kernel - Re: [PATCH 07/14] qcom: mtd: nand: support for passing flags in transfer functions

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Date:   Mon, 10 Jul 2017 19:40:46 +0530
From:   Sricharan R <sricharan@...eaurora.org>
To:     Archit Taneja <architt@...eaurora.org>,
        Abhishek Sahu <absahu@...eaurora.org>, dwmw2@...radead.org,
        computersforpeace@...il.com, boris.brezillon@...e-electrons.com,
        marek.vasut@...il.com, richard@....at, cyrille.pitchen@...ev4u.fr,
        robh+dt@...nel.org, mark.rutland@....com
Cc:     devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
        andy.gross@...aro.org
Subject: Re: [PATCH 07/14] qcom: mtd: nand: support for passing flags in
 transfer functions

Hi,

On 7/4/2017 12:19 PM, Archit Taneja wrote:
> 
> 
> On 06/29/2017 12:45 PM, Abhishek Sahu wrote:
>> The BAM has multiple flags to control the transfer. This patch
>> adds flags parameter in register and data transfer functions and
>> modifies all these function call with appropriate flags.
>>
>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
>> ---
>>   drivers/mtd/nand/qcom_nandc.c | 114 ++++++++++++++++++++++++------------------
>>   1 file changed, 65 insertions(+), 49 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
>> index 7042a65..65c9059 100644
>> --- a/drivers/mtd/nand/qcom_nandc.c
>> +++ b/drivers/mtd/nand/qcom_nandc.c
>> @@ -170,6 +170,14 @@
>>   #define    ECC_BCH_4BIT    BIT(2)
>>   #define    ECC_BCH_8BIT    BIT(3)
>>   +/* Flags used for BAM DMA desc preparation*/
>> +/* Don't set the EOT in current tx sgl */
>> +#define NAND_BAM_NO_EOT            (0x0001)
>> +/* Set the NWD flag in current sgl */
>> +#define NAND_BAM_NWD            (0x0002)
>> +/* Finish writing in the current sgl and start writing in another sgl */
>> +#define NAND_BAM_NEXT_SGL        (0x0004)
>> +
>>   #define QPIC_PER_CW_MAX_CMD_ELEMENTS    (32)
>>   #define QPIC_PER_CW_MAX_CMD_SGL        (32)
>>   #define QPIC_PER_CW_MAX_DATA_SGL    (8)
>> @@ -712,7 +720,7 @@ static int prep_dma_desc(struct qcom_nand_controller *nandc, bool read,
>>    * @num_regs:        number of registers to read
>>    */
>>   static int read_reg_dma(struct qcom_nand_controller *nandc, int first,
>> -            int num_regs)
>> +            int num_regs, unsigned int flags)
>>   {
>>       bool flow_control = false;
>>       void *vaddr;
>> @@ -736,7 +744,7 @@ static int read_reg_dma(struct qcom_nand_controller *nandc, int first,
>>    * @num_regs:        number of registers to write
>>    */
>>   static int write_reg_dma(struct qcom_nand_controller *nandc, int first,
>> -             int num_regs)
>> +             int num_regs, unsigned int flags)
> 
> Adding flags to read_reg_dma and write_reg_dma is making things a bit messy. I can't
> think of a better way to share the code either, though.
> 
> One thing we could consider doing is something like below. I don't know if it would
> make things more legible.
> 
> union nand_dma_props {
>     bool adm_flow_control;
>     unsigned int bam_flags;
> };
> 
> config_cw_read()
> {
>     union nand_dma_props dma_props;
>     ...
>     ...
> 
>     if (is_bam)
>         dma_props.bam_flags = NAND_BAM_NWD;
>     else
>         dma_props.adm_flow_control = false;
> 
>     write_reg_dma(nandc, NAND_EXEC_CMD, 1, &dma_props);
>     ...
>     ...
> }

 Right, with this , i think we can have two different indirections for functions like,
 prep_dma_desc_command and prep_dma_desc. That will help to reduce the bam_dma_enabled
 checks.

Regards,
 Sricharan

-- 
"QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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