Re: [OpenBIOS] [PATCH v4] ppc: SDR1 fixes

[Alexander Graf]

On 21.11.2010, at 21:08, 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.
>
> 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
>
> arch/ppc/qemu/ofmem.c        |   69 ++++++++++++++++++++++++++++-------------
> include/arch/ppc/processor.h |   12 +++++++
> 2 files changed, 59 insertions(+), 22 deletions(-)
>
> diff --git a/arch/ppc/qemu/ofmem.c b/arch/ppc/qemu/ofmem.c
> index 72694b3..6f3079a 100644
> --- a/arch/ppc/qemu/ofmem.c
> +++ b/arch/ppc/qemu/ofmem.c
> @@ -48,7 +48,12 @@ extern void setup_mmu( unsigned long code_base );
> #define OF_CODE_START	0xfff00000UL
> #define IO_BASE			0x80000000
>
> -#define HASH_SIZE		(2 << 15)
> +#ifdef __powerpc64__
> +#define HASH_BITS		18
> +#else
> +#define HASH_BITS		15
> +#endif
> +#define HASH_SIZE		(2 << HASH_BITS)
> #define OFMEM_SIZE		(2 * 1024 * 1024)
>
> #define	SEGR_USER		BIT(2)
> @@ -57,21 +62,11 @@ extern void setup_mmu( unsigned long code_base );
> static inline unsigned long
> get_hash_base( void )
> {
> unsigned long sdr1;
> asm volatile("mfsdr1 %0" : "=r" (sdr1) );
> return (sdr1 & 0xffff0000);
>
> -}
>
> -static inline unsigned long
> -get_hash_size( void )
> -{
> unsigned long sdr1;
> asm volatile("mfsdr1 %0" : "=r" (sdr1) );
> return ((sdr1 << 16) | 0x0000ffff) + 1;
>
> +#ifdef __powerpc64__
> return (mfsdr1() & 0x3FFFFFFFFFFC0000UL);

Just define these as costants and keep the actual code clean :).
> +#else
> return (mfsdr1() & 0xffff0000UL);
>
> +#endif
> }
>
> static inline unsigned long
> @@ -228,6 +223,8 @@ ea_to_phys( ucell ea, ucell *mode )
>    return phys;
> }
>
> +#if defined(__powerpc64__) || defined(CONFIG_PPC_64BITSUPPORT)
>
> static void
> hash_page_64( ucell ea, ucell phys, ucell mode )
> {
> @@ -242,7 +239,7 @@ hash_page_64( ucell ea, ucell phys, ucell mode )
>    vsid = (ea >> 28) + SEGR_BASE;
>    vsid_sh = 7;
>    vsid_mask = 0x00003FFFFFFFFF80ULL;
> asm ( "mfsdr1 %0" : "=r" (sdr) );
> sdr = mfsdr1();
> sdr_sh = 18;
> sdr_mask = 0x3FF80;
> page_mask = 0x0FFFFFFF; // XXX correct?
>
> @@ -294,6 +291,12 @@ hash_page_64( ucell ea, ucell phys, ucell mode )
>    asm volatile( "tlbie %0"  :: "r"(ea) );
> }
>
> +#endif /* ppc64 */
> +#ifndef __powerpc64__
> +/* XXX Turn this into an #else when legacy 64-bit support is gone
> and rename hash_page{32,64} to hash_page.

Just keep them around. They shouldn't hurt. The code will be optimized away by the compiler anyways if CONFIG_PPC_64BITSUPPORT is not set, as static functions that never get caled (if on a constant 0 is never get called) just don't get compiled in.
> */
>
> static void
> hash_page_32( ucell ea, ucell phys, ucell mode )
> {
> @@ -307,7 +310,7 @@ hash_page_32( ucell ea, ucell phys, ucell mode )
>
> hash1 = vsid;
>    hash1 ^= (ea >> 12) & 0xffff;
> hash1 &= (get_hash_size() - 1) >> 6;
>
> hash1 &= (((mfsdr1() & 0x1ff) << 16) | 0xffff) >> 6;
>
> pp = (mPTE_t*)(get_hash_base() + (hash1 << 6));
> upte = (unsigned long*)pp;
>
> @@ -334,6 +337,9 @@ hash_page_32( ucell ea, ucell phys, ucell mode )
>    asm volatile( "tlbie %0"  :: "r"(ea) );
> }
>
> +#endif /* ppc */
> +#ifdef CONFIG_PPC_64BITSUPPORT
>
> static int is_ppc64(void)
> {
>    unsigned int pvr;
> @@ -342,12 +348,21 @@ static int is_ppc64(void)
>    return ((pvr >= 0x330000) && (pvr < 0x70330000));
> }
>
> +#endif /* CONFIG_PPC_64BITSUPPORT */

static int is_ppc64(void)
{
#if defined(__powerpc64__)
    return 1;
#elif defined(CONFIG_PPC_64BITSUPPORT)
    unsigned int pvr = mfpvr();
    return ((pvr >= 0x330000) && (pvr < 0x70330000));
#else
    return 0;
#endif
}
> +/* XXX Drop this function when legacy 64-bit support is dropped. */
> static void hash_page( unsigned long ea, unsigned long phys, ucell mode )
> {
> +#ifdef __powerpc64__
> hash_page_64(ea, phys, mode);
>
> +#else
> +#ifdef CONFIG_PPC_64BITSUPPORT
>    if ( is_ppc64() )
>    	hash_page_64(ea, phys, mode);
>    else
> +#endif
>    	hash_page_32(ea, phys, mode);
> +#endif

if (is_ppc64)
        hash_page_64(ea, phys, mode);
    else
        hash_page_32(ea, phys, mode);
> }
>
> void
> @@ -387,17 +402,27 @@ void
> setup_mmu( unsigned long ramsize )
> {
>    ofmem_t *ofmem;
> unsigned long sdr1, sr_base;
> unsigned long sr_base;
> unsigned long hash_base;
> unsigned long hash_mask = 0xfff00000; /* alignment for ppc64 */
>
> unsigned long hash_mask = ~0x000fffffUL; /* alignment for ppc64 */
> int i;
>
> /* SDR1: Storage Description Register 1 */
>
> hash_base = (ramsize - 0x00100000 - HASH_SIZE) & hash_mask;
> memset((void *)hash_base, 0, HASH_SIZE);
> sdr1 = hash_base | ((HASH_SIZE-1) >> 16);
> asm volatile("mtsdr1 %0" :: "r" (sdr1) );
>
> +#if defined(__powerpc64__) || defined(CONFIG_PPC_64BITSUPPORT)
> +#ifdef CONFIG_PPC_64BITSUPPORT
> if (is_ppc64())
>
> +#endif
> mtsdr1(hash_base | MAX(HASH_BITS - 18, 0));
>
> +#ifdef CONFIG_PPC_64BITSUPPORT
> else
>
> +#endif
> +#endif
> +#ifndef __powerpc64__
> mtsdr1(hash_base | ((HASH_SIZE - 1) >> 16));
>
> +#endif

if (is_ppc64())
        mtsdr1(hash_base | MAX(HASH_BITS - 18, 0));
    else
        mtsdr1(hash_base | (HASH_SIZE - 1) >> 16, 0));

That's a lot easier to read, no?

Alex