Re: [PATCH 1/2] powerpc: add 16K/64K pages support for the 44x PPC32 architectures.

[Hollis Blanchard <hollisb@us.ibm.com>]

On Mon, 2008-11-03 at 15:00 -0500, Josh Boyer wrote:
> On Mon, 03 Nov 2008 13:55:21 -0600
> Hollis Blanchard <hollisb@us.ibm.com> wrote:
> 
> > On Mon, 2008-11-03 at 11:43 +1100, Benjamin Herrenschmidt wrote:
> > > > Cropping the size of the memory node.  That was simplest to do from the
> > > > cuboot wrapper at the time.  If marking it reserved via a reserve map
> > > > is more elegant and correct, we could do that.
> > > > 
> > > > But I will still like to know what about the other way is hairy please.
> > > 
> > > I don't like it :-) Bad feeling ... don't like having a memory
> > > node entry that isn't aligned to some large power of two typically.
> > 
> > More specifically, mm/bootmem.c seems to be making the implicit
> > assumption that memory size is an even multiple of PAGE_SIZE. With 4K
> > pages, 0xffff000 bytes of RAM fits; with 64K pages it does not.
> 
> Hmm..  I dunno what to think about that.  Again, how does mem= play
> into this?  (I will look myself in a bit, but if someone knows offhand
> that would be nice..)
> 
> > Using the device tree reserve map stuff does indeed seem to solve the
> > problem. However, I really don't understand the layering in
> > arch/powerpc/boot at all, so I'll just put this patch out here and
> > people can play with wrappers and prototypes all they want:
> 
> This actually looks pretty nice.  I'll wait for David to Ack the fdt
> parts.

David?

-- 
Hollis Blanchard
IBM Linux Technology Center

> > powerpc/4xx: work around CHIP11 errata in a more PAGE_SIZE-friendly way
> > 
> > The current CHIP11 errata truncates the device tree memory node, and assumes a
> > 4K page size. This breaks kernels with non-4K PAGE_SIZE.
> > 
> > Instead, use a device tree memory reservation to reserve only the 256 bytes
> > actually affected by the errata, leaving the total memory size unaltered.
> > 
> > Signed-off-by: Hollis Blanchard <hollisb@us.ibm.com>
> > 
> > diff --git a/arch/powerpc/boot/4xx.c b/arch/powerpc/boot/4xx.c
> > --- a/arch/powerpc/boot/4xx.c
> > +++ b/arch/powerpc/boot/4xx.c
> > @@ -21,7 +21,7 @@
> >  #include "reg.h"
> >  #include "dcr.h"
> > 
> > -static unsigned long chip_11_errata(unsigned long memsize)
> > +static void chip_11_errata(unsigned long memsize)
> >  {
> >  	unsigned long pvr;
> > 
> > @@ -31,13 +31,11 @@ static unsigned long chip_11_errata(unsi
> >  		case 0x40000850:
> >  		case 0x400008d0:
> >  		case 0x200008d0:
> > -			memsize -= 4096;
> > +			fdt_reserve_mem(memsize - 256, 256);
> >  			break;
> >  		default:
> >  			break;
> >  	}
> > -
> > -	return memsize;
> >  }
> > 
> >  /* Read the 4xx SDRAM controller to get size of system memory. */
> > @@ -53,7 +51,7 @@ void ibm4xx_sdram_fixup_memsize(void)
> >  			memsize += SDRAM_CONFIG_BANK_SIZE(bank_config);
> >  	}
> > 
> > -	memsize = chip_11_errata(memsize);
> > +	chip_11_errata(memsize);
> >  	dt_fixup_memory(0, memsize);
> >  }
> > 
> > @@ -219,7 +217,7 @@ void ibm4xx_denali_fixup_memsize(void)
> >  		bank = 4; /* 4 banks */
> > 
> >  	memsize = cs * (1 << (col+row)) * bank * dpath;
> > -	memsize = chip_11_errata(memsize);
> > +	chip_11_errata(memsize);
> >  	dt_fixup_memory(0, memsize);
> >  }
> > 
> > diff --git a/arch/powerpc/boot/libfdt-wrapper.c b/arch/powerpc/boot/libfdt-wrapper.c
> > --- a/arch/powerpc/boot/libfdt-wrapper.c
> > +++ b/arch/powerpc/boot/libfdt-wrapper.c
> > @@ -167,6 +167,11 @@ static unsigned long fdt_wrapper_finaliz
> >  	return (unsigned long)fdt;
> >  }
> > 
> > +int fdt_reserve_mem(unsigned long addr, unsigned long bytes)
> > +{
> > +	return fdt_add_mem_rsv(fdt, addr, bytes);
> > +}
> > +
> >  void fdt_init(void *blob)
> >  {
> >  	int err;
> > diff --git a/arch/powerpc/boot/ops.h b/arch/powerpc/boot/ops.h
> > --- a/arch/powerpc/boot/ops.h
> > +++ b/arch/powerpc/boot/ops.h
> > @@ -83,6 +83,7 @@ extern struct loader_info loader_info;
> > 
> >  void start(void);
> >  void fdt_init(void *blob);
> > +int fdt_reserve_mem(unsigned long addr, unsigned long bytes);
> >  int serial_console_init(void);
> >  int ns16550_console_init(void *devp, struct serial_console_data *scdp);
> >  int mpsc_console_init(void *devp, struct serial_console_data *scdp);
> > 
> >