[U-Boot] [PATCHv2 5/8] drivers: mtd: spi: Modify read/write command for sfl256s flash.

[Sourav Poddar <sourav.poddar@ti.com>]

Hi Jagan,
On Wednesday 31 July 2013 12:23 PM, Sourav Poddar wrote:
> Hi Jagan,
> On Tuesday 23 July 2013 07:53 PM, Sourav Poddar wrote:
>> + jagan,
>>
>> On Tuesday 23 July 2013 02:29 PM, Sourav Poddar wrote:
>>> Reading using the already supported read command is causing regression
>>> after 4k bytes, as a result doing a page by page read. Its 
>>> happening, because
>>> ti qpsi controller CS will get de asserted after 4096 bytes.
>>>
>>> Signed-off-by: Sourav Poddar<sourav.poddar@ti.com>
>>> ---
>>>   drivers/mtd/spi/spi_flash.c |   32 +++++++++++++++++++++++++++++++-
>>>   1 files changed, 31 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
>>> index 6a6fe37..5f8db7b 100644
>>> --- a/drivers/mtd/spi/spi_flash.c
>>> +++ b/drivers/mtd/spi/spi_flash.c
>>> @@ -303,6 +303,36 @@ int spi_flash_cmd_read_fast(struct spi_flash 
>>> *flash, u32 offset,
>>>           else
>>>               read_len = remain_len;
>>>
>>> +#ifdef CONFIG_TI_QSPI
>>> +        unsigned long page_addr, byte_addr, page_size;
>>> +        size_t chunk_len, actual;
>>> +        int ret = 0;
>>> +
>>> +        page_size = flash->page_size;
>>> +        page_addr = offset / page_size;
>>> +        byte_addr = offset % page_size;
>>> +
>>> +        for (actual = 0; actual<  read_len; actual += chunk_len) {
>>> +            chunk_len = min(read_len - actual, page_size - byte_addr);
>>> +
>>> +            cmd[1] = page_addr>>  8;
>>> +            cmd[2] = page_addr;
>>> +            cmd[3] = byte_addr;
>>> +
>>> +            ret = spi_flash_read_common(flash, cmd, sizeof(cmd),
>>> +                    data + actual, chunk_len);
>>> +            if (ret<  0) {
>>> +                debug("SF: read failed");
>>> +                break;
>>> +            }
>>> +
>>> +            byte_addr += chunk_len;
>>> +            if (byte_addr == page_size) {
>>> +                page_addr++;
>>> +                byte_addr = 0;
>>> +            }
>>> +        }
>>> +#else
>>>           spi_flash_addr(offset, cmd);
>>>
>>>           ret = spi_flash_read_common(flash, cmd, sizeof(cmd),
>>> @@ -311,7 +341,7 @@ int spi_flash_cmd_read_fast(struct spi_flash 
>>> *flash, u32 offset,
>>>               debug("SF: read failed\n");
>>>               break;
>>>           }
>>> -
>>> +#endif
>>>           offset += read_len;
>>>           len -= read_len;
>>>           data += read_len;
>> Elaborating a bit more on this,
>> There is a constrain on our hardware, which goes like this..
>>
>> As soon as the words transfered is 4096 bytes, the CS gets deasserted 
>> automatically.
>> As a result of this bottleneck, I am not able to use the current use 
>> read api in mtd framework.
>> This requires me to send the read command every time in range upto 
>> 4096 bytes only.
>>
>> To overcome this, I have updated the mtd read based on TI_QSPI config 
>> as done above.
>>
>> [Jagan]:
>> Do you have any suggestion of dealing this in a better way?
>> I don't see a way to get around this apart from updating mtd read 
>> depending on TI_QSPI config.
>>
> Any inputs on this?
>

Any suggestions on the patch?