[U-Boot] [PATCH] cmd_sf: add handler for +len arg for all commands

[Chin Liang See]

On Sun, 2014-10-05 at 22:55 +0200, marex at denx.de wrote:
> On Sunday, October 05, 2014 at 10:35:06 PM, Maxime Hadjinlian wrote:
> > On Sun, Oct 5, 2014 at 10:28 PM, Marek Vasut <marex at denx.de> wrote:
> > > On Sunday, October 05, 2014 at 09:51:27 PM, Maxime Hadjinlian wrote:
> > >> On Sun, Oct 5, 2014 at 9:45 PM, Marek Vasut <marex at denx.de> wrote:
> > >> > On Sunday, October 05, 2014 at 09:27:00 PM, Maxime Hadjinlian wrote:
> > >> >> On Sun, Oct 5, 2014 at 9:19 PM,  <thomas.langer at lantiq.com> wrote:
> > >> >> >> On Sunday, October 05, 2014 at 08:40:26 PM, Maxime Hadjinlian wrote:
> > >> >> >> > Hi Thomas, all,
> > >> >> >> > 
> > >> >> >> > On Sun, Oct 5, 2014 at 7:43 PM,  <thomas.langer at lantiq.com> wrote:
> > >> >> >> > > Hello Maxime,
> > >> >> >> > > 
> > >> >> >> > > can you explain the usecase?
> > >> >> >> > > I think, only the erase is executed per sector, all other
> > >> >> >> > > commands are working fine with a byte oriented length.
> > >> >> >> > 
> > >> >> >> > I need to write a file that is downloaded through TFTP. So I can
> > >> >> >> > get the filesize through the variable of the same name, but if
> > >> >> >> > it's not rounded, the write command may fail.
> > >> >> >> > I can save the filesize in another variable, but at next boot,
> > >> >> >> > when I need to read this file, I can't read the file, since I
> > >> >> >> > only know it's size in byte, I need to be able to round it
> > >> >> >> > again.
> > >> >> >> 
> > >> >> >> I wonder, do all SPI flashes need to do sector-aligned writes ?
> > >> >> > 
> > >> >> > All the serial flashes I have seen so far do support reading and
> > >> >> > writing with any length, independent from the erase size.
> > >> >> > Otherwise the current implementation of env_sf.c would also not
> > >> >> > work.
> > >> >> 
> > >> >> Well the QSPI, I used, does not. Every read and write has to be
> > >> >> aligned. That's why I needed that in the first place.
> > >> > 
> > >> > Aligned how exactly?
> > >> 
> > >> sector-aligned.
> > >> If I write anything that is not sector aligned, the 'sf' command will
> > >> fail.
> > > 
> > > Is that really a property of the SPI flash or the SPI controller ? And if
> > > the later, is it a property of a particular one or is that a common
> > > thing ?
> > 
> > I'll have to check but if I remember correctly, it's the SPI flash.
> > It's a Micron Serial NOR flash (N25Q512A83G1240x).
> > And the controller is the Cadence QSPI controller available on the SoC
> > FPGA platform.
> > Maybe what caused my issues was the driver after all ?
> 
> +CC Altera guys, they might help too.

Hmmm.... quite strange to write for sector aligned.
Wonder the write related to filesystem access?

Within Cadence QSPI controller, read and write access need to be done
within a page. But that would be taken care by controller when the
access beyond the next page. From software perspective, we just tell
controller the numbers of bytes to be transfer (for indirect transfer
setup).

Chin Liang

> 
> Best regards,
> Marek Vasut