[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 <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...

Andreas