[U-Boot] [PATCH] sf: Enable FSR polling on N25Q256(A)

[Marek Vasut]

On 05/29/2018 06:52 AM, Jagan Teki wrote:
> + Siva
> 
> On Fri, May 25, 2018 at 1:28 AM, Marek Vasut <marex at denx.de> wrote:
>> The N25Q256(A) datasheet clearly states that this device does have
>> a Flag Status Register and does update FSR PEC bit 7 during Program
>> and Erase cycles to indicate the cycle is in progress. Enable the
>> FSR PEC bit polling on this device to prevent data corruption.
>>
>> Signed-off-by: Marek Vasut <marex at denx.de>
>> Cc: Jagan Teki <jagan at openedev.com>
>> Cc: Tom Rini <trini at konsulko.com>
>> ---
>>  drivers/mtd/spi/spi_flash_ids.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/spi/spi_flash_ids.c b/drivers/mtd/spi/spi_flash_ids.c
>> index 3b8f254ca2..fbc1bb6a5e 100644
>> --- a/drivers/mtd/spi/spi_flash_ids.c
>> +++ b/drivers/mtd/spi/spi_flash_ids.c
>> @@ -130,8 +130,8 @@ const struct spi_flash_info spi_flash_ids[] = {
>>         {"n25q64a",        INFO(0x20bb17, 0x0,  64 * 1024,   128, RD_FULL | WR_QPP | SECT_4K) },
>>         {"n25q128",        INFO(0x20ba18, 0x0,  64 * 1024,   256, RD_FULL | WR_QPP) },
>>         {"n25q128a",       INFO(0x20bb18, 0x0,  64 * 1024,   256, RD_FULL | WR_QPP) },
>> -       {"n25q256",        INFO(0x20ba19, 0x0,  64 * 1024,   512, RD_FULL | WR_QPP | SECT_4K) },
>> -       {"n25q256a",       INFO(0x20bb19, 0x0,  64 * 1024,   512, RD_FULL | WR_QPP | SECT_4K) },
>> +       {"n25q256",        INFO(0x20ba19, 0x0,  64 * 1024,   512, RD_FULL | WR_QPP | E_FSR | SECT_4K) },
>> +       {"n25q256a",       INFO(0x20bb19, 0x0,  64 * 1024,   512, RD_FULL | WR_QPP | E_FSR | SECT_4K) },
> 
> FSR is required to poll flag status instead of read status only from
> Micron n25q512 because 512 is divided into two 256 dies so FSR is used
> for polling each die. In case of n25q256 the flash is single entity
> (doesn't have die concept) so there is no need to poll FSR.
> 
> This is what I understood when I add initial FSR support
> 0f6232801cee4f45dbdb0cec45f71172c9b617ca

The datasheet for N25Q256A (which is probably a better reference than a
commit in the U-Boot tree) claims the FSR is an indication of
PROGRAM/ERASE completion. We use SR and FSR (if it is avaiable) to check
whether all of the SNOR operations finished, so if FSR is available, we
should use it. Plus, I have an impression that the SR polling is not
reliable on the N25Q256A.

-- 
Best regards,
Marek Vasut