[U-Boot] [PATCH v2 2/2] mtd: add altera quadspi driver

Jagan Teki
2015-11-06T09:52:04Z

Hi Thomas,

On 6 November 2015 at 14:58, Thomas Chou <thomas@wytron.com.tw> wrote:
> Hi Jagan,
>
> On 2015?11?06? 16:07, Jagan Teki wrote:
>>
>> I appreciate your hardware expertise and am not questioning about that
>> as well. I do agree with the hw logic about altera qspi controller and
>> I don't have any questions with hw either.
>>
>> But my main intention here was about the software support since Linux
>> discussed about this subject and finally moved to spi-nor controllers
>> (though they don't use spi bus at-all) to spi-nor framework and Marek
>> knows this topic very well.
>>
>> I believe discussion about this topic much more clear if we send this
>> driver to Linux.
>
>
> Sorry that I was absent and didn't know about the topic discussed on Linux.
> The purpose of u-boot and Linux is quite different thought they may share
> some code. The drivers are different, too. Whatever they chose on Linux is
> not related here.

I'm trying to interface the same standard wrt Linux stack, So adding
new features is reasonable and easy for developers to send the patches
if we have same stand-point as what Linux or vice-versa. Yes drivers
are bit different wrt Linux ie OK, anyway we need to implement with
dm-driven but the functionality flow will be same like

Linux --> u-boot
mtd_utils --> cmd_sf
mtd_info -->mtd_info
spi-nor --> spi-nor
m25p80.c --> spi-nor-flash (dm-driven)
fsl-quadspi --> fsl-qspi (dm-driven)

Finally, what is the main issue if we move to spi-nor instead of cfi?
agreed that it never used generic spi but even if it there in spi-nor
also it never used generic spi, spi-nor should also use mtd as cfi and
also it's serial flash it should be part of spi-nor that make more
sense to me.

>
> Marek did agree that "The behavior of this device is closer to CFI flash.".
> This is what the core designed for, to replace the CFI flash. I am more
> concerned with users. Users can use memory commands to display and modify
> the content directly. This is very point where the driver should stand.

Yes from uses point of view, it's a cfi flash but generally all cfi's
are parallel in nature so it's shouldn't treated as serial. If we use
sf user at least thought he would doing serial flash operations.

thanks!
--
Jagan | openedev.