Re: dw_spi CS control/transfer modes

[Feng Tang <feng.tang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

Hi Jamie,

On Sat, 19 Mar 2011 04:11:35 +0800
Jamie Iles <jamie-wmLquQDDieKakBO8gow8eQ@public.gmane.org> wrote:

> Hi,
> 
> I have a platform with a DesignWare SSI and I'm trying to use the
> dw_spi block using a GPIO for the chip select to workaround the
> problem of CS changing and the device losing state (we have a SPI
> flash attached), and I've found that using interrupt driven
> transfers, reading the SPI flash results in very few interrupts from
> the controller and a sluggish system (and no data from the flash).
> 
> However, I've found that removing the conditional transfer mode
> setting (effectively reverting commit 052dc7c45 [spi/dw_spi:
> conditional transfer mode changes]) allows everything to work fine by
> keeping the transfer mode to transmit+receive.

What version of code are you using? The "cs_control" will be default to
NULL if "dw_spi_chip" as the controller data doesn't explicitly set it,
and then that piece of code won't be called.

Thanks,
Feng

> 
> Does anyone have any ideas on the best way to fix this?  That code
> must have been added for a reason so perhaps it's just a quirk on our 
> platform, but I'd be keen to know in what ways it's been tested
> before - afaict, no other in-tree platforms are using dw_spi with
> their own cs_control so it's difficult to know if perhaps these are
> all doing polled mode transfers.
> 
> Thanks,
> 
> Jamie
> 
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