diff options
Diffstat (limited to 'src/soc/nvidia/tegra124/clock.c')
| -rw-r--r-- | src/soc/nvidia/tegra124/clock.c | 68 |
1 files changed, 40 insertions, 28 deletions
diff --git a/src/soc/nvidia/tegra124/clock.c b/src/soc/nvidia/tegra124/clock.c index 765e447ecb..eed5116c32 100644 --- a/src/soc/nvidia/tegra124/clock.c +++ b/src/soc/nvidia/tegra124/clock.c @@ -304,18 +304,17 @@ clock_display(u32 frequency) * = (cf * n) >> p, where 1MHz < cf < 6MHz * = ((ref / m) * n) >> p * - * Assume p = 0, find (m, n). since m has only 5 bits, we can iterate - * all possible values. Note Tegra 124 supports 11 bits for n, but our - * pll_fields has only 10 bits for n. + * Assume p = 0, find best (m, n). since m has only 5 bits, we can + * iterate all possible values. Note Tegra 124 supports 11 bits for n, + * but our pll_fields has only 10 bits for n. * * Note values undershoot or overshoot target output frequency may not - * work if the value is not in "safe" range in panel specification, so - * we want exact match. + * work if the values are not in "safe" range by panel specification. */ - struct pllpad_dividers plld = { 0 }; u32 ref = clock_get_pll_input_khz() * 1000, m, n; u32 cf, vco = frequency; + u32 diff, best_diff = vco; const u32 max_m = 1 << 5, max_n = 1 << 10, mhz = 1000 * 1000, min_vco = 500 * mhz, max_vco = 1000 * mhz, min_cf = 1 * mhz, max_cf = 6 * mhz; @@ -326,40 +325,53 @@ clock_display(u32 frequency) return -1; } - for (m = 1; m < max_m; m++) { + for (m = 1; m < max_m && best_diff; m++) { cf = ref / m; if (cf < min_cf) break; + if (cf > max_cf) + continue; n = vco / cf; - if (vco != cf * n || n >= max_n || cf > max_cf) + if (n >= max_n) + continue; + + diff = vco - n * cf; + if (n + 1 < max_n && diff > cf / 2) { + n++; + diff = cf - diff; + } + + if (diff >= best_diff) continue; + best_diff = diff; plld.m = m; plld.n = n; + } + + if (plld.n < 50) + plld.cpcon = 2; + else if (plld.n < 300) + plld.cpcon = 3; + else if (plld.n < 600) + plld.cpcon = 8; + else + plld.cpcon = 12; - if (n < 50) - plld.cpcon = 2; - else if (n < 300) - plld.cpcon = 3; - else if (n < 600) - plld.cpcon = 8; - else - plld.cpcon = 12; - - printk(BIOS_DEBUG, "%s: PLLD=%u ref=%u, m/n/p/cpcon=" - "%u/%u/%u/%u\n", __func__, - (ref / plld.m * plld.n) >> plld.p, ref, - plld.m, plld.n, plld.p, plld.cpcon); - - init_pll(&clk_rst->plld_base, &clk_rst->plld_misc, plld, - (PLLUD_MISC_LOCK_ENABLE | PLLD_MISC_CLK_ENABLE)); - return 0; + if (best_diff) { + printk(BIOS_ERR, "%s: Failed to match output frequency %u, " + "best difference is %u.\n", __func__, frequency, + best_diff); } - printk(BIOS_ERR, "%s: Failed to match output frequency %u.\n", - __func__, frequency); - return -1; + printk(BIOS_DEBUG, "%s: PLLD=%u ref=%u, m/n/p/cpcon=%u/%u/%u/%u\n", + __func__, (ref / plld.m * plld.n) >> plld.p, ref, plld.m, plld.n, + plld.p, plld.cpcon); + + init_pll(&clk_rst->plld_base, &clk_rst->plld_misc, plld, + (PLLUD_MISC_LOCK_ENABLE | PLLD_MISC_CLK_ENABLE)); + return 0; } /* Initialize the UART and put it on CLK_M so we can use it during clock_init(). |