[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 07 August 2013 05:21 PM, Jagan Teki wrote:
> Hi,
>
> On Wed, Aug 7, 2013 at 11:27 AM, Sourav Poddar<sourav.poddar@ti.com>  wrote:
>> 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?
>>
>> _______________________________________________
>> U-Boot mailing list
>> U-Boot at lists.denx.de
>> http://lists.denx.de/mailman/listinfo/u-boot
> Yes, this part is pretty much working as with other s25fl.
> Can you point me the respective controller driver for this.
>
Thanks for the response.

This is the link to uboot patches which I submitted to uboot mailing list.

http://patchwork.ozlabs.org/patch/260989/
http://patchwork.ozlabs.org/patch/260990/
http://patchwork.ozlabs.org/patch/260991/
http://patchwork.ozlabs.org/patch/260992/
http://patchwork.ozlabs.org/patch/260994/
http://patchwork.ozlabs.org/patch/260993/
http://patchwork.ozlabs.org/patch/260996/
http://patchwork.ozlabs.org/patch/260995/

Above are the links to uboot patches containing all def configs and 
uboot ti qspi driver.

As communicated earlier, there is a limitation in our qspi controller 
driver, wherein after every
4096 bytes CS gets de asserted. So, I had to modify the above read 
framework to do a page read.
Need better way to handle this limitation, so that the above patch 
series can get upstreamed.
> Does linux support this ti_qspi, please point the defconfig if you have.
>
Patches for linux is under review and still not mainlined.
https://patchwork.kernel.org/patch/2838342/

Thanks,
Sourav
> --
> Thanks,
> Jagan.