[U-Boot] [PATCH 03/18] sf: fix sf probe

[Tom Rini <trini@ti.com>]

On Mon, Aug 04, 2014 at 04:45:57PM +0300, Nikita Kiryanov wrote:
> 
> 
> On 04/08/14 16:10, Marek Vasut wrote:
> >On Monday, August 04, 2014 at 02:48:54 PM, Nikita Kiryanov wrote:
> >>Hi Marek,
> >>
> >>On 03/08/14 16:46, Marek Vasut wrote:
> >>>On Sunday, August 03, 2014 at 09:34:33 AM, Nikita Kiryanov wrote:
> >>>>MXC SPI driver has a feature whereas a GPIO line can be used as a CS
> >>>>signal. This is set up by joining the CS and GPIO values into a single
> >>>>value using (cs | gpio << 8), and passing it off as a CS value. This
> >>>>breaks the sf probe command, because it is no longer possible to invoke
> >>>>it as sf probe <cs>. Instead, the user must use sf probe <cs | gpio <<
> >>>>8>.
> >>>>
> >>>>Fix this by introducing a new board function: board_spi_cs_gpio().
> >>>>When called, board_spi_cs_gpio() will return the gpio number for the
> >>>>cs value it is given.
> >>>>
> >>>>Cc: Jagannadha Sutradharudu Teki <jagannadh.teki@gmail.com>
> >>>>Cc: Eric Nelson <eric.nelson@boundarydevices.com>
> >>>>Cc: Eric Benard <eric@eukrea.com>
> >>>>Cc: Fabio Estevam <fabio.estevam@freescale.com>
> >>>>Cc: Tim Harvey <tharvey@gateworks.com>
> >>>>Cc: Stefano Babic <sbabic@denx.de>
> >>>>Cc: Tom Rini <trini@ti.com>
> >>>>Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
> >>>
> >>>Just curious, but is this fixing generic SF code or MXC SPI driver ? I'd
> >>>think the later, but it's not obvious from neither the description nor
> >>>the subject. I don't quite understand the problem that you're trying to
> >>>fix either, what happened, did the user command interface change ?
> >>
> >>The U-Boot shell command "sf probe" can accept a chip select value, but
> >>if the SPI device on the other end requires an active chip-select over
> >>multiple transactions (achieved in the MXC SPI driver using a GPIO),
> >>simply typing something like "sf probe 0" will not work.
> >
> >Why not ?
> >
> >>This is because whatever the user passes as chip select is propagated
> >>to the driver, and the driver expects this value to have GPIO
> >>information. So for example, if IMX_GPIO_NR(2, 30) is used to force
> >>active chip select 0, then instead of "sf probe 0" the user will have
> >>to type "sf probe 15872".
> >
> >You mean sf probe 0:15872 , right ?
> 
> It's the same thing:
> sf probe [[bus:]cs] [hz] [mode]
> 
> The point is that cs 0 has to be represented as "15872", instead of "0".

Eeep.  That seems very likely to be gotten incorrect by users.

Can we do something like:
mxc_spi.c:
__weak int board_map_spi_cs_value(int desired_cs) { return -EINVAL; }

fooboard.c:
board_map_spi_cs_value(int desired_cs) {
  if (desired_cs == 0)
    return IMX_GPIO_NR(2, 30);
  else
    return -EINVAL;
}

I think it'll be very bad if the user has to type 'sf probe 0:15872' or
'sf probe 15872' since that's a programming detail rather than saying
bank 2, gpio 30 (which I assume is what IMX_GPIO_NR means).

-- 
Tom
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