[U-Boot] [PATCH 1/2] arm: sunxi: allwinner spi driver sun6i support

[Andre Przywara]

On Thu, 24 Jan 2019 11:17:03 +0100
Alexander Graf <agraf at suse.de> wrote:

> On 22.01.19 17:37, Alexander Graf wrote:
> > 
> > 
> > On 22.01.19 17:28, Alexander Graf wrote:  
> >>
> >>
> >> On 22.01.19 17:17, Oskari Lemmelä wrote:  
> >>> Hi,
> >>>
> >>> On 22.1.2019 16.54, Alexander Graf wrote:  
> >>>>
> >>>> On 05.01.19 18:52, Oskari Lemmela wrote:  
> >>>>> Minimal changes to support sun6i based Allwinner SOCs
> >>>>> Changes are based to SPL driver
> >>>>> arch/arm/mach-sunxi/spl_spi_sunxi.c
> >>>>>
> >>>>> Signed-off-by: Oskari Lemmela <oskari at lemmela.net>  
> >>>> I just tried to see if this patch gives me "sf" access on a
> >>>> SoPine system. Unfortunately, it seems as if the sun4i_spi
> >>>> driver doesn't even get probed?
> >>>>
> >>>> How did you manage to actually make use of this driver?
> >>>>
> >>>>
> >>>> Alex  
> >>>
> >>> You need to add spi0 alias to dts and enable needed drivers to
> >>> defconfig. You can take look from Jagan's patch [1].
> >>>
> >>> I didn't include those changes as Maxime already commented [2]
> >>> that Kconfig depends/defaults should be modified first.  
> >>
> >> I don't see any relation between the dts change and the Kconfig
> >> dependency issues?
> >>
> >> But thanks for the pointer, I'll give this patch a try.  
> > 
> > Ok, so I now get the SPI controller initialized, but it seems to
> > only returns zeros when trying to access the SPI flash device.
> > 
> > In other words, it doesn't work for me :). But maybe I'm missing
> > all the other clk patches to actually get it working?  
> 
> Ok, so turns out the problem is that you can't have eMMC and SPI both
> working. I don't quite know yet whether this is just a pinmux problem
> (so potentially software workaroundable) or if it's a hardware
> limitation (eMMC pulling a line required for SPI).

The line that is shared is "DS", which is only needed for higher (e)MMC
modes (HS-400). At the moment neither Linux nor U-Boot implement this
mode, and probably U-Boot will never need it: it adds software
complexity for a questionable performance benefit, especially if the
flash chips can't keep up with the high interface speed anyway.

We addressed this in the DTs (kernel commit fa59dd2ef755).

I am a bit puzzled here as why this happens: I can't find where U-Boot
would configure PC1 to use the MMC2 function: the hard-coded
mmc_pinmux_setup() doesn't touch PC1 at all. Maybe it's the BootROM
configuring this line? So we would need to reset it?

As I don't have an eMMC module here at hand right now, this has to wait
till tonight for further insights.

> But either way, without the eMMC module, things seem to work:
> 
>   Tested-by: Alexander Graf <agraf at suse.de>

Does anyone care to clean up the Kconfig dependency mess, since we seem
to know all the options we need now? Ideally we would just need one or
two symbols in the *_defconfig files, the rest being automatically
selected by Kconfig magic.
It's on my list, but there are other things higher on that one.

Cheers,
Andre.