[U-Boot] [PATCH V6] sf: Turn SPI flash chip into 3-Byte address mode

[Siva Durga Prasad Paladugu]

> -----Original Message-----
> From: Stefan Roese [mailto:sr at denx.de]
> Sent: Thursday, August 13, 2015 4:51 PM
> To: Hou Zhiqiang; Siva Durga Prasad Paladugu; u-boot at lists.denx.de;
> jteki at openedev.com
> Cc: nofooter; York Sun
> Subject: Re: [U-Boot] [PATCH V6] sf: Turn SPI flash chip into 3-Byte address
> mode
>
> On 13.08.2015 12:50, Hou Zhiqiang wrote:
> >> -----Original Message-----
> >> From: Siva Durga Prasad Paladugu
> >> [mailto:siva.durga.paladugu at xilinx.com]
> >> Sent: 2015年8月13日 17:18
> >> To: Hou Zhiqiang-B48286; u-boot at lists.denx.de; jteki at openedev.com
> >> Cc: Sun York-R58495; Hu Mingkai-B21284; nofooter
> >> Subject: RE: [PATCH V6] sf: Turn SPI flash chip into 3-Byte address
> >> mode
> >>
> >> Hi Zhejiang/Jagan,
> >>
> >> I think it would be good to extend this further to support 4-byte
> >> addressing in u-boot also.
> >> This would be based on the driver, We can get the data that whether
> >> the controller supports 4-byte or not from the driver level(through
> >> slave
> >> struct) and enable 4 byte addressing here based on that.
> >>
> >
> > That is a long way, and I don't think it is necessary for U-Boot. The
> > U-Boot work well using BAR to address more than 16MiB flash.
> > This patch focus on the address mode issue when warm boot up base on
> > the BAR address mode.
>
> Please correct me if I'm wrong, but AFAIU this BAR thing
> (CONFIG_SPI_FLASH_BAR) doesn't support to address e.g. a 64MiB SPI flash
> contiguously. Only 16MiB areas. So for example its not possible to put
> UBI/UBIFS in such a big partition.
>
> I have to support Siva here. We really should try to support this 4-byte mode
> correctly. This can't be too hard.

Yeah, I think it wouldn't be too difficult to add support for 4-byte address.
we may just need to bypass the SPI_FLASH_BAR in read_ops , write_ops and erase_ops routines.

This support need not be part of this series. It can be a separate series. As we already added routine to disable /enable 4 byte as a part of this,
I just shared that it would be good to have 4 byte support also.


Regards,
Siva
>
> Thanks,
> Stefan



This email and any attachments are intended for the sole use of the named recipient(s) and contain(s) confidential information that may be proprietary, privileged or copyrighted under applicable law. If you are not the intended recipient, do not read, copy, or forward this email message or any attachments. Delete this email message and any attachments immediately.