Re: [PATCH/RFC 0/4] sh-sci : Do not derive regshift from regsize

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Monday, 6 August 2018 17:37:45 EEST Laurent Pinchart wrote:
> On Monday, 6 August 2018 17:07:51 EEST Geert Uytterhoeven wrote:
> > 	Hi all,
> > 
> > This RFC patch series was sparked by noticing that commit 2d4dd0da45401c7a
> 
> Where can that commit be found ?

I found it in -next, sorry for the noise.

> > ("serial: sh-sci: Allow for compressed SCIF address") broke earlycon
> > support on most Renesas ARM SoCs using SCIF ports, and by the fragility of
> 
> > deriving regshift from the register block size (which may be rounded up):
> 
> Why should it be rounded up ?
> 
> >   1. The first patch is an old patch from Sato-san, which I never really
> >      understood.  But it turned out to be a dependency for patch 2.
> >   2. Patch 2 makes sure regshift is initialized when using earlycon,
> >      unbreaking the serial console on e.g. R-Car Gen2 and Gen3.
> >   3. Patch 3 reverts the patch that started deriving regshift from the
> >      register block size, and that removed the plat_sci_port.regshift
> >      field.  Which is a field I needed again in patch 4.
> >   4. Patch 4 removes the remaining regshift derivations on DT platforms.
> >  (5. I didn't bother writing patch 5, which involves adding .regshift
> >      initializations to all SH board files that need it.)
> > 
> > However, I'm not happy with the end result, so please DO NOT apply this!
> > As I spent almost a full day on this, and would still like to know the
> > story about "sh-sci: Use a separate sci_port for earlycon", I decided to
> > post it anyway.
> > 
> > As earlycon will be broken in v4.19-rc1 on RZ/A1, RZ/G, and R-Car,
> > assuming
> > 
> > no other actions are taken, an alternative solution would be to:
> >   1. Revert commit 7acece71a517cad8 ("serial: sh-sci: Remove
> >      SCIx_RZ_SCIFA_REGTYPE"),
> >   2. Revert commit 2d4dd0da45401c7a ("serial: sh-sci: Allow for compressed
> >      SCIF address") alternative,
> >   3. Add an OF_EARLYCON_DECLARE() for RZ/A2, to fix earlycon on RZ/A2.
> > 
> > What do you think?
> > Thanks for your comments!
> > 
> > P.S. Apparently SCIx_SH4_SCIF_REGTYPE and SCIx_SH2_SCIF_FIFODATA_REGTYPE
> > 
> >      are identical?
> > 
> > Geert Uytterhoeven (3):
> >   [RFC] sh-sci: Take into account regshift to fix earlycon breakage
> >   [RFC] Revert "serial: sh-sci: Compute the regshift value for SCI
> >     ports"
> >   [RFC] sh-sci: Derive regshift value from DT compatible value
> > 
> > Yoshinori Sato (1):
> >   [RFC] sh-sci: Use a separate sci_port for earlycon
> >  
> >  arch/sh/kernel/cpu/sh3/setup-sh770x.c |  1 +
> >  arch/sh/kernel/cpu/sh4/setup-sh7750.c |  3 +-
> >  arch/sh/kernel/cpu/sh4/setup-sh7760.c | 10 +---
> >  drivers/tty/serial/sh-sci.c           | 68 +++++++++++++++++----------
> >  include/linux/serial_sci.h            |  1 +
> >  5 files changed, 49 insertions(+), 34 deletions(-)

-- 
Regards,

Laurent Pinchart