Re: [OpenBIOS] [PATCH v5] ppc: SDR1 fixes

[Andreas Färber]

Am 22.11.2010 um 00:46 schrieb Alexander Graf:
> On 22.11.2010, at 00:14, Andreas Färber   
> wrote:
> > Clean up use of SDR1 fields.
> >
> > IBM's "The Programming Environments for 32-Bit Microprocessors":
> > The HTABMASK field in SDR1 contains a mask value that determines
> > how many bits from the hash are used in the page table index. This  
> > mask
> > must be of the form 0b00...011...1; that is, a string of 0 bits  
> > followed by
> > a string of 1bits. The 1 bits determine how many additional bits  
> > (at least 10)
> > from the hash are used in the index; HTABORG must have this same  
> > number of
> > low-order bits equal to 0.
> >
> > IBM's "The Programming Environments Manual for 64-bit  
> > Microprocessors" 3.0:
> > The HTABSIZE field in SDR1 contains an integer value that determines
> > how many bits from the hash are used in the page table index. This  
> > number
> > must not exceed 28. HTABSIZE is used to generate a mask of the form
> > 0b00...011...1; that is, a string of 0 bits followed by a string of  
> > 1-bits.
> > The 1-bits determine how many additional bits (beyond the minimum  
> > of 11)
> > from the hash are used in the index. The HTABORG must have this  
> > same number
> > of low-order bits equal to 0.
> >
> > Adjust alignment mask and hash size for ppc64.
> >
> > Note that the page table does not yet scale with the memory size, and
> > the secondary hash is not yet used.
> >
> > v5:
> > Move HTABORG mask to header.
> > Keep is_ppc64() for now, suggested by Alex.
> >
> > Merge CONFIG_PPC_64BITSUPPORT handling here so that it behaves as  
> > intended,
> > not recognizing a ppc64 CPU in pure 32-bit mode.
> > Stub out hash_page_32() for ppc64 to avoid having to care about
> >
> > it for ppc64.
> > hash_page_64() is less critical for pure ppc build since the code  
> > needs to be
> > 32-bit compatible anyway.
> >
> > v4:
> > Don't redefine hash_page_{32,64} but add TODO comments for
> >
> > renaming.
> > Keep and simplify hash_page().
> >
> > v3:
> > Fix shifts. Thanks to Segher and Alex.
> > Fix HTABSIZE for 32-bit ppc64: ((2 << 15) - 1) >> 16 happened to
> >
> > be 0,
> > so that it worked as expected. Avoid underflow, spotted by Alex.
> > Make this fix available for legacy 64-bit support as well.
> > Drop get_hash_size(). It was only used in hash_page_32() and caused
> >
> > unnecessary conversions between HTABMASK and size.
> > Introduce {mfsdr1,mtsdr1} as suggested by Alex.
> >
> > Note that this changes the volatility for hash_page_64().
> > Conditionalize 64-bit support, drop 32-bit support for ppc64.
> > Adjust hash size for ppc64.
> >
> > v2:
> > Use HTABSIZE for ppc64, fix HTABMASK usage for ppc.
> >
> > Error spotted by Segher.
> >
> > Cc: Alexander Graf 
> > Cc: Segher Boessenkool 
> > Signed-off-by: Andreas Färber
>
> This one looks a lot cleaner. I don't see any obvious glitches  
> either, so:
>
> Signed-off-by: Alexander Graf

Phew... thanks! Applied as r967.

A rather unproductive weekend unfortunately, no progress in gdb yet...

Andreas