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skl_compute_wrpll: Don't try other dividers if we find a 0 central freq deviation

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Paulo suggested that we could short-circuit the search for a good
divider if we find a 0 deviation of the DCO frequency from the central
frequency.

Out of the 373 test frequencies, 34 hit that fast path.

Suggested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
This commit is contained in:
Damien Lespiau 2015-06-25 17:38:19 +01:00
parent 26336385ac
commit de774ed31e
1 changed files with 18 additions and 5 deletions
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19
tools/skl_compute_wrpll.c
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@ -274,7 +274,12 @@ static void skl_wrpll_context_init(struct skl_wrpll_context *ctx)
#define SKL_MAX_PDEVIATION 100
#define SKL_MAX_NDEVIATION 600
static void skl_wrpll_try_divider(struct skl_wrpll_context *ctx,
/*
* Returns true if we're sure to have found the definitive divider (ie
* deviation == 0).
*/
static bool skl_wrpll_try_divider(struct skl_wrpll_context *ctx,
uint64_t central_freq,
uint64_t dco_freq,
unsigned int divider)
@ -297,6 +302,10 @@ static void skl_wrpll_try_divider(struct skl_wrpll_context *ctx,
found = true;
#endif
}
/* we can't improve a 0 deviation */
if (deviation == 0)
return true;
/* negative deviation */
} else if (deviation < SKL_MAX_NDEVIATION &&
deviation < ctx->min_deviation) {
@ -315,6 +324,8 @@ static void skl_wrpll_try_divider(struct skl_wrpll_context *ctx,
printf("dco_freq: %"PRIu64", dco_central_freq %"PRIu64"\n",
dco_freq, central_freq);
}
return false;
}
static void skl_wrpll_get_multipliers(unsigned int p,
@ -433,13 +444,15 @@ skl_ddi_calculate_wrpll2(int clock /* in Hz */,
unsigned int p = dividers[d].list[i];
uint64_t dco_freq = p * afe_clock;
skl_wrpll_try_divider(&ctx,
if (skl_wrpll_try_divider(&ctx,
dco_central_freq[dco],
dco_freq,
p);
p))
goto skip_remaining_dividers;
}
}
skip_remaining_dividers:
/*
* If a solution is found with an even divider, prefer
* this one.