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SubjectRe: [PATCH v2 02/25] mtd: nand: qcom: program NAND_DEV_CMD_VLD register
On 2017-08-03 21:17, Boris Brezillon wrote:
> On Wed, 19 Jul 2017 17:17:50 +0530
> Abhishek Sahu <absahu@codeaurora.org> wrote:
>
>> The current driver is failing without complete bootchain since
>> NAND_DEV_CMD_VLD value is not valid.
>>
>> Signed-off-by: Abhishek Sahu <absahu@codeaurora.org>
>> ---
>> drivers/mtd/nand/qcom_nandc.c | 4 ++++
>> 1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/mtd/nand/qcom_nandc.c
>> b/drivers/mtd/nand/qcom_nandc.c
>> index bc0408c..f3b995d 100644
>> --- a/drivers/mtd/nand/qcom_nandc.c
>> +++ b/drivers/mtd/nand/qcom_nandc.c
>> @@ -148,6 +148,9 @@
>> #define FETCH_ID 0xb
>> #define RESET_DEVICE 0xd
>>
>> +/* Value for NAND_DEV_CMD_VLD */
>> +#define NAND_DEV_CMD_VLD_VAL 0x1d
>
> Where does this 0x1d value comes from? Defining a macro instead of
> passing 0x1d does not change the fact that this is a magic value :-).
>

This register tells the NAND controller which commands are valid

Bits Meaning
0 READ_START_VALID
1 READ_STOP_VALID
2 WRITE_START_VALID
3 ERASE_START_VALID
4 SEQ_READ_START_VLD

The default power on value is
0xe - ERASE_START_VALID | WRITE_START_VALID | READ_STOP_VALID

It need to be programmed for
0x1d - READ_START_VALID | WRITE_START_VALID | ERASE_START_VALID |
SEQ_READ_START_VLD

Read STOP command is not required in normal NAND reads so it need to be
disabled.

I will define the individual bits and will make this value with bits
which will
make this more clear.

>> +
>> /*
>> * the NAND controller performs reads/writes with ECC in 516 byte
>> chunks.
>> * the driver calls the chunks 'step' or 'codeword' interchangeably
>> @@ -1972,6 +1975,7 @@ static int qcom_nandc_setup(struct
>> qcom_nand_controller *nandc)
>> {
>> /* kill onenand */
>> nandc_write(nandc, SFLASHC_BURST_CFG, 0);
>> + nandc_write(nandc, NAND_DEV_CMD_VLD, NAND_DEV_CMD_VLD_VAL);
>>
>> /* enable ADM DMA */
>> nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);

--
Abhishek Sahu

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