Re: [LinuxBIOS] [PATCH] Geode LX CAS setting fix

[ron minnich]

Acked-by: Ronald G. Minnich

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  wrote:
> See attached patch.
> Thanks!
> Marc
>
> 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
> 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;
>   }