Revision(s) Affected:

AM65x SR 1.0

Details:

The VTM_TMPSENSj_STAT[9-0] DTEMP, where j = 0-7, registers can be read in software to determine the last sampled temperature of each of the ‘j’ number of on die temp sensors on the SoC. If a read happens on the same exact cycle that a temperature sample is updated then there is a chance that the read data can be corrupted due to incorrect resynchronization between clock domains.

Workaround(s):

Software should perform three reads from the VTM_TMPSENSj_STAT[9-0] DTEMP, where j = 0-7, registers. Software should then compute the temperature to be used based on the average of the two samples that are closest to each other.

The software pseudo code is as follows:

#define abs(x) (((x)<0)?-(x):(x)) 
unsigned int get_best_value(unsigned int s0, unsigned int s1, unsigned int s2) 
{ 
        int d01 = abs(s0 - s1); 
        int d02 = abs(s0 - s2); 
        int d12 = abs(s1 - s2); 
                         
        // if delta 01 is least, take 0 and 1 
        if ((d01 <= d02) && (d01 <=d12)) { 
                return (s0+s1)/2; 
        } 
        // if delta 02 is least, take 0 and 2 
        if ((d02 <= d01) && (d02 <=d12)) { 
                return (s0+s2)/2; 
        } 
        /* in all other cases, take 1 and 2 */ 
        return (s1+s2)/2; 
} 
  
unsigned int get_temp() 
{ 
        unsigned int s0,s1,s2; 
        s0 = Read VTM_TMPSENSj_STAT[9-0] DTEMP; 
        s1 = Read VTM_TMPSENSj_STAT[9-0] DTEMP; 
        s2 = Read VTM_TMPSENSj_STAT[9-0] DTEMP; 
        return get_best_value(s0,s1,s2); 
}