[U-Boot] [PATCH 3/7] eSPI: add eSPI controller support

[Hu Mingkai-B21284]

> -----Original Message-----
> From: Mike Frysinger [mailto:vapier at gentoo.org] 
> Sent: Monday, March 16, 2009 3:28 PM
> To: u-boot at lists.denx.de
> Cc: Jean-Christophe PLAGNIOL-VILLARD; Hu Mingkai-B21284; 
> Fleming Andy-AFLEMING
> Subject: Re: [U-Boot] [PATCH 3/7] eSPI: add eSPI controller support
> 
> On Monday 16 March 2009 02:15:27 Jean-Christophe 
> PLAGNIOL-VILLARD wrote:
> > On 10:52 Mon 16 Mar     , Mingkai Hu wrote:
> > > Add eSPI controller support under the SPI framework.
> > >
> > > Signed-off-by: Mingkai Hu <Mingkai.hu at freescale.com>
> > > ---
> > >  drivers/mtd/spi/spi_flash.c |   94 +++++++++++++++++-
> > >  drivers/spi/Makefile        |    1 +
> > >  drivers/spi/fsl_espi.c      |  232
> > > +++++++++++++++++++++++++++++++++++++++++++ include/spi.h 
>               |
> > >   30 ++++++
> > >  4 files changed, 354 insertions(+), 3 deletions(-)  create mode 
> > > 100644 drivers/spi/fsl_espi.c
> >
> > please use the spi framework, their is no need to touch the 
> spi_flash 
> > support ti add and use the fsl_espi
> 
> indeed ... i was so happy to see the spansion driver i 
> glossed over this ... 
> those spi_flash.c changes are almost assuredly wrong and 
> indicate you arent fitting into the framework correctly.
> -mike
> 

There is difference between the SPI and eSPI chip select signal.
Generally, the SPI chip select is controlled by GPIO, so SW can control
when to
assert the chip select signal and when to stop the chip select signal.
But the eSPI controller integrate the chip select into the controller
itself, it use the
transfer length to control the duration of the chip select signal.

The spi_flash_cmd_* function split the transfer into two steps: first
the command
transfer and then the data transfer. At the first step, the transfer
length is set to
the command length, and when transferred the command, the chip select
will be
negated, so the eSPI controller thinks the transfer is cancelled and
doesn't transfer
the data again.

I'm in a dilemma on this issue and really need your suggestion :-)

Thanks,
Mingkai