[U-Boot] [PATCH] ARM: mvebu: db-88f6820-amc: enable SPI_FLASH_BAR

[Stefan Roese]

Hi Vignesh,

On 02.03.19 11:50, Vignesh Raghavendra wrote:
> Hi Stefan,
> 
> On 02-Mar-19 3:56 PM, Stefan Roese wrote:
>> Hi Chris,
>> Hi Vignesh,
>>
>> On 02.03.19 09:36, Vignesh Raghavendra wrote:
>>>
>>>
>>> On 02-Mar-19 1:15 PM, Chris Packham wrote:
>>>> This board uses Micron N25Q256A SPI flash. Enable SPI_FLASH_BAR to allow
>>>> us to access the whole chip.
>>>>
>>>> Signed-off-by: Chris Packham <judge.packham at gmail.com>
>>>> Cc: Vignesh R <vigneshr at ti.com>
>>>> ---
>>>>
>>>
>>> Could add imply SPI_FLASH_BAR to KIRKWOOD_SPI instead? So that we don't
>>> have to fix every defconfig that using kirkwood_spi.c.
>>
>> Did you use BAR before the newly introduced SPI NOR restructuring?
>> If not, then I would rather oppose to using it now, since option
>> should only be used by those platforms that used it earlier as well.
> 
> configs/db-88f6820-amc_defconfig did use SPI_FLASH_BAR before SPI NOR
> re-work

I see. Thanks for checking.
  
>> BAR mode is not supported by Linux and an U-Boot special.
>>    
>>> Looks like kernel driver does support 3/4 byte addressing, but U-Boot
>>> version of the driver doesn't.
>>
>> Could you please double check, if and how addressing of the whole
>> 32MiB was done before? And perhaps its possible to enhance the SPI
>> driver to support 3 and 4 byte addressing instead.
>>
> 
> It would be great if driver could be modified to support 3 and 4 byte
> addressing modes.

I fail to see, what really is needed to make the SPI driver support
3 and 4 byte addressing modes. I recently added the MT7688 SPI
driver (mt7621_spi.c) which supports 3 and 4 byte mode and I remember
no driver specials that I needed to implement for this feature. Its
address mode agnostic AFAICT and just xfers a buffer of data to and
from the SPI device.

Could you please let me know, what exactly is missing for this 4 byte
mode?

Thanks,
Stefan