[PATCHv2] drivers: mtd: devices: Add quad read support.

[Sourav Poddar]

On Friday 27 September 2013 11:46 AM, Huang Shijie wrote:
> 于 2013年09月27日 13:54, Sourav Poddar 写道:
>> On Friday 27 September 2013 08:10 AM, Huang Shijie wrote:
>>> 于 2013年09月26日 19:21, Sourav Poddar 写道:
>>>> If the pupose of LUT is to just set the dummy cycles, and vf610-twr
>>>> hardware state machine does not have have any other dependency
>>>> on LUT, this patch should work.
>>> Hi Sourav & David:
>>>
>>>    The key issue about the vf610-twr is that:
>>>    [0] Use the LUT makes the Quadspi driver more efficiency.
>>>    [1] the vf610-twr needs to know the SPI NOR commands for Page 
>>> Program.
>>>        Why? because the driver can not change the size of 
>>> write-buffer from 256bytes to the 64byte(TXFIFO SIZE).
>> Not clear about this. But, you will anyway know what you are using 
>> from the m25p80 side rite?
>
>  The TX FIFO is 64 bytes in the Vybrid, but the Page Program may 
> writes 265 bytes per time.
>
>  If the TX FIFO is smaller then the size of Page Program, we have to 
> wait until the Write(64bytes) is finished.
>  If we do not wait, the write will not finished.
>
>
hmm..I think thats should be handle in your controller by checking 
t->tx_buf and see what command is used.
>
>>>    [2] the dummy and other things.
>>>
>> Dummy stuffs can be handled from m25p80 side rite? fast read dummy 
>> cycle support is already there. While,
>> $subject patch adds it for quad read.
> The m25p80 can only handle the 8bit dummy now, such as fast read and 
> QOR(0x6b).
>
> But it can not handle the QIOR (0XEB, may needs 4bit dummy), and can 
> not handle the DDR QIOR(0XED, may
> needs 6bit dummy).
>
Correct, as I explained in one of my comment on v1, that the creating of 
a quad api is justified for this reason itself, since
there are other quad commands wth different dummy cycle requirements. We 
can build on top of $subject patch and try
to add support for other quad commands also. ?
> thanks
> Huang Shijie
>