[OpenBIOS] [PATCH v5] ppc: SDR1 fixes

[Alexander Graf]

On 22.11.2010, at 21:20, Andreas Färber wrote:

> Am 22.11.2010 um 00:46 schrieb Alexander Graf:
> 
>> On 22.11.2010, at 00:14, Andreas Färber <andreas.faerber at web.de> 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 <agraf at suse.de>
>>> Cc: Segher Boessenkool <segher at kernel.crashing.org>
>>> Signed-off-by: Andreas Färber <andreas.faerber at web.de>
>> 
>> This one looks a lot cleaner. I don't see any obvious glitches either, so:
>> 
>> Signed-off-by: Alexander Graf <agraf at suse.de>
> 
> Phew... thanks! Applied as r967.
> 
> A rather unproductive weekend unfortunately, no progress in gdb yet...

Sorry for making you go through so many iterations :). One thing came to mind still: Please make sure that you take into account that the page table size is different for ppc64-on-ppc32 than the define inclines. If anything needs to know the real htab size, you need to have that one call a function that find it out for real.


Alex