[LinuxBIOS] [PATCH] Geode LX CAS setting fix

[ron minnich]

Acked-by: Ronald G. Minnich <rminnich at gmail.com>

Note: I have not tested this on hardware. But I can bet Marc has :-)
This just convinces me that DRAM really is black magic :-)

On 6/13/07, Marc Jones <marc.jones at amd.com> wrote:
> See attached patch.
> Thanks!
> Marc
>
> --
> Marc Jones
> Senior Software Engineer
> (970) 226-9684 Office
> mailto:Marc.Jones at amd.com
> http://www.amd.com/embeddedprocessors
>
> This patch fixes the CAS map for -.5 and -1 CAS settings. The -.5 setting should only shift the mask one bit, not two.
>
> Signed-off-by: Marc Jones <marc.jones at amd.com>
>
>
> Index: LinuxBIOSv2/src/northbridge/amd/lx/raminit.c
> ===================================================================
> --- LinuxBIOSv2.orig/src/northbridge/amd/lx/raminit.c   2007-06-13 17:01:03.000000000 -0600
> +++ LinuxBIOSv2/src/northbridge/amd/lx/raminit.c        2007-06-13 17:01:03.000000000 -0600
> @@ -151,7 +151,7 @@
>         }
>
>         /* I don't think you need this check.
> -          if (spd_byte0 < 0xA0 || spd_byte0 < 0xA0){
> +          if (spd_byte0 >= 0xA0 || spd_byte1 >= 0xA0){
>            print_debug("DIMM overclocked. Check GeodeLink Speed\n");
>            POST_CODE(POST_PLL_MEM_FAIL);
>            __asm__       __volatile__("hlt\n");
> @@ -231,7 +231,7 @@
>  ;*     Destroys: We really use everything !
>  ;*****************************************************************************/
>         uint16_t glspeed, dimm_speed;
> -       uint8_t spd_byte, casmap0, casmap1;
> +       uint8_t spd_byte, casmap0, casmap1, casmap_shift;
>         msr_t msr;
>
>         glspeed = GeodeLinkSpeed();
> @@ -246,25 +246,24 @@
>                         dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) +
>                                                 (spd_byte & 0x0F)));
>                         if (dimm_speed >= glspeed) {
> +                               casmap_shift = 1; /* -.5 is a shift of 1 */
>                                 /* IF -1 timing is supported, check -1 timing > GeodeLink */
>                                 spd_byte = spd_read_byte(DIMM0, SPD_SDRAM_CYCLE_TIME_3RD);
>                                 if (spd_byte != 0) {
>                                         /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
>                                         dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F)));
> -                                       if (dimm_speed <= glspeed) {
> -                                               /* set we can use -.5 timing but not -1 */
> -                                               spd_byte = 31 - __builtin_clz((uint32_t) casmap0);
> -                                               /* just want bits in the lower byte since we have to cast to a 32 */
> -                                               casmap0 &= 0xFF << (--spd_byte);
> +                                       if (dimm_speed >= glspeed) {
> +                                               casmap_shift = 2; /* -1 is a shift of 2 */
>                                         }
> -                               }       /*MIN_CYCLE_10 !=0 */
> +                               }       /* SPD_SDRAM_CYCLE_TIME_3RD (-1) !=0 */
>                         } else {
> -                               /* Timing_05 < GLspeed, can't use -.5 or -1 timing */
> -                               spd_byte = 31 - __builtin_clz((uint32_t) casmap0);
> -                               /* just want bits in the lower byte since we have to cast to a 32 */
> -                               casmap0 &= 0xFF << (spd_byte);
> +                               casmap_shift = 0;
>                         }
> -               }               /*MIN_CYCLE_05 !=0 */
> +               }       /* SPD_SDRAM_CYCLE_TIME_2ND (-.5) !=0 */
> +               /* set the casmap based on the shift to limit possible CAS settings */
> +               spd_byte = 31 - __builtin_clz((uint32_t) casmap0);
> +               /* just want bits in the lower byte since we have to cast to a 32 */
> +               casmap0 &= 0xFF << (spd_byte - casmap_shift);
>         } else {                /* No DIMM */
>                 casmap0 = 0;
>         }
> @@ -278,25 +277,25 @@
>                         /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
>                         dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F)));
>                         if (dimm_speed >= glspeed) {
> +                               casmap_shift = 1; /* -.5 is a shift of 1 */
>                                 /* IF -1 timing is supported, check -1 timing > GeodeLink */
>                                 spd_byte = spd_read_byte(DIMM1, SPD_SDRAM_CYCLE_TIME_3RD);
>                                 if (spd_byte != 0) {
>                                         /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
>                                         dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F)));
> -                                       if (dimm_speed <= glspeed) {
> -                                               /* set we can use -.5 timing but not -1 */
> -                                               spd_byte = 31 - __builtin_clz((uint32_t) casmap1);
> -                                               /* just want bits in the lower byte since we have to cast to a 32 */
> -                                               casmap1 &= 0xFF << (--spd_byte);
> +                                       if (dimm_speed >= glspeed) {
> +                                               casmap_shift = 2; /* -1 is a shift of 2 */
>                                         }
> -                               }       /*MIN_CYCLE_10 !=0 */
> +                                       /* note that the -1 result doesn't need to change the available CAS map */
> +                               }       /* SPD_SDRAM_CYCLE_TIME_3RD (-1) !=0 */
>                         } else {
> -                               /* Timing_05 < GLspeed, can't use -.5 or -1 timing */
> -                               spd_byte = 31 - __builtin_clz((uint32_t) casmap1);
> -                               /* just want bits in the lower byte since we have to cast to a 32 */
> -                               casmap1 &= 0xFF << (spd_byte);
> +                               casmap_shift = 0;
>                         }
> -               }               /*MIN_CYCLE_05 !=0 */
> +               }       /* SPD_SDRAM_CYCLE_TIME_2ND (-.5) !=0 */
> +               /* set the casmap based on the shift to limit possible CAS settings */
> +               spd_byte = 31 - __builtin_clz((uint32_t) casmap1);
> +               /* just want bits in the lower byte since we have to cast to a 32 */
> +               casmap1 &= 0xFF << (spd_byte - casmap_shift);
>         } else {                /* No DIMM */
>                 casmap1 = 0;
>         }
>
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