Re: [PATCH 2/2] powerpc/83xx: map IMMR with a BAT.

[Christophe Leroy]

Le 14/09/2019 Ã 16:34, Scott Wood a ÃcritÂ:
> On Fri, 2019-08-23 at 12:50 +0000, Christophe Leroy wrote:
> > On mpc83xx with a QE, IMMR is 2Mbytes.
> > On mpc83xx without a QE, IMMR is 1Mbytes.
> > Each driver will map a part of it to access the registers it needs.
> > Some driver will map the same part of IMMR as other drivers.
> >
> > In order to reduce TLB misses, map the full IMMR with a BAT.
> >
> > Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
> > ---
> >   arch/powerpc/platforms/83xx/misc.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/powerpc/platforms/83xx/misc.c
> > b/arch/powerpc/platforms/83xx/misc.c
> > index f46d7bf3b140..1e395b01c535 100644
> > --- a/arch/powerpc/platforms/83xx/misc.c
> > +++ b/arch/powerpc/platforms/83xx/misc.c
> > @@ -18,6 +18,8 @@
> >   #include <sysdev/fsl_soc.h>
> >   #include <sysdev/fsl_pci.h>
> >   
> > +#include <mm/mmu_decl.h>
> > +
> >   #include "mpc83xx.h"
> >   
> >   static __be32 __iomem *restart_reg_base;
> > @@ -145,6 +147,14 @@ void __init mpc83xx_setup_arch(void)
> >   	if (ppc_md.progress)
> >   		ppc_md.progress("mpc83xx_setup_arch()", 0);
> >   
> > +	if (!__map_without_bats) {
> > +		int immrsize = IS_ENABLED(CONFIG_QUICC_ENGINE) ? SZ_2M :
> > SZ_1M;
>
> Any reason not to unconditionally make it 2M?  After all, the kernel being
> built with CONFIG_QUICC_ENGINE doesn't mean that the hardware you're running
> on has it...

Euh .. ok. I didn't see it that way, but you are right.

Do you think it is not a problem to map 2M even when the quicc engine is 
not there ? Or should it check device tree instead ?

Christophe