[U-Boot] [PATCH 03/16] spi: Add non DM version of SPI_MEM

[Boris Brezillon <boris.brezillon@bootlin.com>]

On Thu, 13 Dec 2018 02:15:16 +0530
Jagan Teki <jagan@amarulasolutions.com> wrote:

> On Thu, Dec 13, 2018 at 2:10 AM Boris Brezillon
> <boris.brezillon@bootlin.com> wrote:
> >
> > Hi Jagan,
> >
> > On Thu, 13 Dec 2018 01:55:08 +0530
> > Jagan Teki <jagan@amarulasolutions.com> wrote:
> >  
> > > On Wed, Dec 12, 2018 at 11:08 PM Vignesh R <vigneshr@ti.com> wrote:  
> > > >
> > > > Add non DM version of SPI_MEM to support easy migration to new SPI NOR
> > > > framework. This can be removed once DM_SPI conversion is complete.  
> > >
> > > Our intention to use new driver to follow dm, why we need to support
> > > non-dm? any usecases?  
> >
> > Looks like we're having the same discussion over and over. Vignesh is
> > dropping spi_flash.c which AFAICT was not depending on DM_SPI, so, if
> > we want to keep everyone happy while getting rid of some legacy code,
> > that's the only solution. DM conversion is a nice goal, but it's kind
> > of orthogonal to what Vignesh is working on. If DM_SPI conversion
> > happens before the spi-nor stuff is merged  (which I doubt) then this
> > patch can simply be dropped.  
> 
> spi_flash.c is a core code not a specific driver it belongs. spi-mem
> is new feature driver how come new driver will support legacy non-dm
> do we have legacy use for that(ie what I'm asking about usecase)

I recommend that you read the spi-mem code carefully. spi-mem is not
driver specific, it's a thin layer on top of spi and driver *can* (but
are not forced to) provide optimized methods to execute spi-mem
operations. When that's not the case, the implementation falls back to
regular spi transfers. AFAIK, both DM and non-DM drivers support
regular spi transfers, right? So why should we depend on DM_SPI? And
more importantly, if we do that, that means we can't get rid of
spi_flash.c since some users might still have non-DM SPI drivers, which
in turn means we keep more legacy code for no good reasons.

You want non-DM SPI controller drivers to go away, then remove them,
instead of blocking other changes using this excuse.