+ outpdimm->lowest_common_spd_caslat = caslat_actual;
+ debug("lowest_common_spd_caslat is 0x%x\n", caslat_actual);
+
+ return 0;
+}
+#else /* for DDR1 and DDR2 */
+static unsigned int
+compute_cas_latency(const unsigned int ctrl_num,
+ const dimm_params_t *dimm_params,
+ common_timing_params_t *outpdimm,
+ unsigned int number_of_dimms)
+{
+ int i;
+ const unsigned int mclk_ps = get_memory_clk_period_ps(ctrl_num);
+ unsigned int lowest_good_caslat;
+ unsigned int not_ok;
+ unsigned int temp1, temp2;
+
+ debug("using mclk_ps = %u\n", mclk_ps);
+ if (mclk_ps > outpdimm->tckmax_ps) {
+ printf("Warning: DDR clock (%u ps) is slower than DIMM(s) (tCKmax %u ps)\n",
+ mclk_ps, outpdimm->tckmax_ps);
+ }
+
+ /*
+ * Compute a CAS latency suitable for all DIMMs
+ *
+ * Strategy for SPD-defined latencies: compute only
+ * CAS latency defined by all DIMMs.
+ */
+
+ /*
+ * Step 1: find CAS latency common to all DIMMs using bitwise
+ * operation.
+ */
+ temp1 = 0xFF;
+ for (i = 0; i < number_of_dimms; i++) {
+ if (dimm_params[i].n_ranks) {
+ temp2 = 0;
+ temp2 |= 1 << dimm_params[i].caslat_x;
+ temp2 |= 1 << dimm_params[i].caslat_x_minus_1;
+ temp2 |= 1 << dimm_params[i].caslat_x_minus_2;
+ /*
+ * If there was no entry for X-2 (X-1) in
+ * the SPD, then caslat_x_minus_2
+ * (caslat_x_minus_1) contains either 255 or
+ * 0xFFFFFFFF because that's what the glorious
+ * __ilog2 function returns for an input of 0.
+ * On 32-bit PowerPC, left shift counts with bit
+ * 26 set (that the value of 255 or 0xFFFFFFFF
+ * will have), cause the destination register to
+ * be 0. That is why this works.
+ */
+ temp1 &= temp2;
+ }
+ }
+
+ /*
+ * Step 2: check each common CAS latency against tCK of each
+ * DIMM's SPD.
+ */
+ lowest_good_caslat = 0;
+ temp2 = 0;
+ while (temp1) {
+ not_ok = 0;
+ temp2 = __ilog2(temp1);
+ debug("checking common caslat = %u\n", temp2);
+
+ /* Check if this CAS latency will work on all DIMMs at tCK. */
+ for (i = 0; i < number_of_dimms; i++) {
+ if (!dimm_params[i].n_ranks)
+ continue;
+
+ if (dimm_params[i].caslat_x == temp2) {
+ if (mclk_ps >= dimm_params[i].tckmin_x_ps) {
+ debug("CL = %u ok on DIMM %u at tCK=%u ps with tCKmin_X_ps of %u\n",
+ temp2, i, mclk_ps,
+ dimm_params[i].tckmin_x_ps);
+ continue;
+ } else {
+ not_ok++;
+ }
+ }
+
+ if (dimm_params[i].caslat_x_minus_1 == temp2) {
+ unsigned int tckmin_x_minus_1_ps
+ = dimm_params[i].tckmin_x_minus_1_ps;
+ if (mclk_ps >= tckmin_x_minus_1_ps) {
+ debug("CL = %u ok on DIMM %u at tCK=%u ps with tckmin_x_minus_1_ps of %u\n",
+ temp2, i, mclk_ps,
+ tckmin_x_minus_1_ps);
+ continue;
+ } else {
+ not_ok++;
+ }
+ }
+
+ if (dimm_params[i].caslat_x_minus_2 == temp2) {
+ unsigned int tckmin_x_minus_2_ps
+ = dimm_params[i].tckmin_x_minus_2_ps;
+ if (mclk_ps >= tckmin_x_minus_2_ps) {
+ debug("CL = %u ok on DIMM %u at tCK=%u ps with tckmin_x_minus_2_ps of %u\n",
+ temp2, i, mclk_ps,
+ tckmin_x_minus_2_ps);
+ continue;
+ } else {
+ not_ok++;
+ }
+ }
+ }
+
+ if (!not_ok)
+ lowest_good_caslat = temp2;
+
+ temp1 &= ~(1 << temp2);
+ }
+
+ debug("lowest common SPD-defined CAS latency = %u\n",
+ lowest_good_caslat);
+ outpdimm->lowest_common_spd_caslat = lowest_good_caslat;
+
+
+ /*
+ * Compute a common 'de-rated' CAS latency.
+ *
+ * The strategy here is to find the *highest* dereated cas latency
+ * with the assumption that all of the DIMMs will support a dereated
+ * CAS latency higher than or equal to their lowest dereated value.
+ */
+ temp1 = 0;
+ for (i = 0; i < number_of_dimms; i++)
+ temp1 = max(temp1, dimm_params[i].caslat_lowest_derated);
+
+ outpdimm->highest_common_derated_caslat = temp1;
+ debug("highest common dereated CAS latency = %u\n", temp1);
projects / u-boot.git / blobdiff