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

[Jagan Teki]

On Wed, Aug 7, 2013 at 5:34 PM, Sourav Poddar <sourav.poddar at ti.com> wrote:
> 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 at 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 at 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, please give me some time I will look at these and let u know
early next week.

--
Thanks,
Jagan.