Re: [PATCH 09/14] qcom: mtd: nand: BAM support for read page

[Sricharan R]

Hi,

On 7/4/2017 3:10 PM, Archit Taneja wrote:
> 
> 
> On 06/29/2017 12:46 PM, Abhishek Sahu wrote:
>> 1. The BAM mode requires few registers configuration before each
>>     NAND page read and codeword read which is different from ADM
>>     so add the helper functions which will be called in BAM mode
>>     only.
>>
>> 2. The NAND page read handling of BAM is different from ADM so
>>     call the appropriate helper functions
>>
>> Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx>
>> ---
>>   drivers/mtd/nand/qcom_nandc.c | 63 ++++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 62 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
>> index 8e7dc9e..17766af 100644
>> --- a/drivers/mtd/nand/qcom_nandc.c
>> +++ b/drivers/mtd/nand/qcom_nandc.c
>> @@ -870,6 +870,35 @@ static void config_cw_read(struct qcom_nand_controller *nandc)
>>   }
>>     /*
>> + * Helpers to prepare DMA descriptors for configuring registers
>> + * before reading a NAND page with BAM.
>> + */
>> +static void config_bam_page_read(struct qcom_nand_controller *nandc)
>> +{
>> +    write_reg_dma(nandc, NAND_FLASH_CMD, 3, 0);
>> +    write_reg_dma(nandc, NAND_DEV0_CFG0, 3, 0);
>> +    write_reg_dma(nandc, NAND_EBI2_ECC_BUF_CFG, 1, 0);
>> +    write_reg_dma(nandc, NAND_ERASED_CW_DETECT_CFG, 1, 0);
>> +    write_reg_dma(nandc, NAND_ERASED_CW_DETECT_CFG, 1,
>> +              NAND_ERASED_CW_SET | NAND_BAM_NEXT_SGL);
>> +}
>> +
>> +/*
>> + * Helpers to prepare DMA descriptors for configuring registers
>> + * before reading each codeword in NAND page with BAM.
>> + */
> 
> If I understood right, EBI2 nand required us to load all the registers
> configured in config_cw_read() for every codeword, and for BAM, the
> registers configured in config_bam_page_read() just needs to be done once,
> and the registers in config_bam_cw_read()  need to be reloaded for every
> codeword?
> 
> Could you please clarify this better in the commit message and comments? Also,
> I still see config_cw_read() being used for QPIC nand in nandc_param() and
> copy_last_cw()?
> 
> Also, I think these should be called config_qpic_page_read() and
> config_qpic_cw_read() since it seems more of a property of the NAND controller
> rather than the underlying DMA engine. If so, config_cw_read() can be called
> config_cw_ebi2_read(). Please correct me if I'm wrong somewhere.
> 

 Even here as well, if we have different function pointers for config_bam_cw_read
 and config_cw_read for bam, adm, we can still share code with helpers and have
 only the difference populated in to those functions, reducing the if (bam_dma_enabled)
 checks.

Regards,
 Sricharan



>> +static void config_bam_cw_read(struct qcom_nand_controller *nandc)
>> +{
>> +    write_reg_dma(nandc, NAND_READ_LOCATION_0, 2, 0);
>> +    write_reg_dma(nandc, NAND_FLASH_CMD, 1, NAND_BAM_NEXT_SGL);
>> +    write_reg_dma(nandc, NAND_EXEC_CMD, 1, NAND_BAM_NEXT_SGL);
>> +
>> +    read_reg_dma(nandc, NAND_FLASH_STATUS, 2, 0);
>> +    read_reg_dma(nandc, NAND_ERASED_CW_DETECT_STATUS, 1,
>> +             NAND_BAM_NEXT_SGL);
>> +}
>> +
>> +/*
>>    * helpers to prepare dma descriptors used to configure registers needed for
>>    * writing a codeword/step in a page
>>    */
>> @@ -1398,6 +1427,9 @@ static int read_page_ecc(struct qcom_nand_host *host, u8 *data_buf,
>>       struct nand_ecc_ctrl *ecc = &chip->ecc;
>>       int i, ret;
>>   +    if (nandc->dma_bam_enabled)
>> +        config_bam_page_read(nandc);
>> +
>>       /* queue cmd descs for each codeword */
>>       for (i = 0; i < ecc->steps; i++) {
>>           int data_size, oob_size;
>> @@ -1411,7 +1443,36 @@ static int read_page_ecc(struct qcom_nand_host *host, u8 *data_buf,
>>               oob_size = host->ecc_bytes_hw + host->spare_bytes;
>>           }
>>   -        config_cw_read(nandc);
>> +        if (nandc->dma_bam_enabled) {
>> +            if (data_buf && oob_buf) {
>> +                nandc_set_reg(nandc, NAND_READ_LOCATION_0,
>> +                          (0 << READ_LOCATION_OFFSET) |
>> +                          (data_size <<
>> +                          READ_LOCATION_SIZE) |
>> +                          (0 << READ_LOCATION_LAST));
>> +                nandc_set_reg(nandc, NAND_READ_LOCATION_1,
>> +                          (data_size <<
>> +                          READ_LOCATION_OFFSET) |
>> +                          (oob_size << READ_LOCATION_SIZE) |
>> +                          (1 << READ_LOCATION_LAST));
>> +            } else if (data_buf) {
>> +                nandc_set_reg(nandc, NAND_READ_LOCATION_0,
>> +                          (0 << READ_LOCATION_OFFSET) |
>> +                          (data_size <<
>> +                          READ_LOCATION_SIZE) |
>> +                          (1 << READ_LOCATION_LAST));
>> +            } else {
>> +                nandc_set_reg(nandc, NAND_READ_LOCATION_0,
>> +                          (data_size <<
>> +                          READ_LOCATION_OFFSET) |
>> +                          (oob_size << READ_LOCATION_SIZE) |
>> +                          (1 << READ_LOCATION_LAST));
>> +            }
> 
> Could we put the READ_LOCATION_x register configuration into a small helper?
> This is probably a matter of taste, but you could consider configuring like this.
> Maybe something similar for patch #11 for raw page reads.
> 
>     if (data_buf && oob_buf) {
>         r0_off = 0;
>         r0_size = r1_off = data_size;
>         r1_size = oob_size;
>         r0_last = 0;
>         r1_last = 1;
>     } else if (data_buf) {
>         rl0_off = 0;
>         rl0_size = data_size;
>         rl0_last = 1;
>     } else {
>         rl0_off = data_size;
>         rl0_size = oob_size;
>         rl0_last = 1;
>     }
> 
>     nandc_set_reg(nandc, NAND_READ_LOCATION_0,
>               (rl0_off << READ_LOCATION_OFFSET) |
>               (rl0_size << READ_LOCATION_SIZE) |
>               (rl0_last << READ_LOCATION_LAST));
>     if (rl1_last)
>         /* program LOCATION_1 register */
> 
> Thanks,
> Archit
> 
>> +
>> +            config_bam_cw_read(nandc);
>> +        } else {
>> +            config_cw_read(nandc);
>> +        }
>>             if (data_buf)
>>               read_data_dma(nandc, FLASH_BUF_ACC, data_buf,
>>
> 

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