We can't improve a 0 deviation, so when we find such a divider, skip the
remaining ones they won't be better.
This short-circuit the search for 34 of the 373 test frequencies in the
corresponding i-g-t test (tools/skl_compute_wrpll)
Suggested-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Signed-off-by: Damien Lespiau <damien.lespiau@xxxxxxxxx>
---
This patch has to be applied after patch 12 and 13 for the recent SKL DPLL
series.
drivers/gpu/drm/i915/intel_ddi.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
index f6b3ccc..45116d8 100644
--- a/drivers/gpu/drm/i915/intel_ddi.c
+++ b/drivers/gpu/drm/i915/intel_ddi.c
@@ -1122,7 +1122,11 @@ static void skl_wrpll_context_init(struct skl_wrpll_context *ctx)
#define SKL_DCO_MAX_PDEVIATION 100
#define SKL_DCO_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)
@@ -1141,6 +1145,10 @@ static void skl_wrpll_try_divider(struct skl_wrpll_context *ctx,
ctx->dco_freq = dco_freq;
ctx->p = divider;
}
+
+ /* we can't improve a 0 deviation */
+ if (deviation == 0)
+ return true;
/* negative deviation */
} else if (deviation < SKL_DCO_MAX_NDEVIATION &&
deviation < ctx->min_deviation) {
@@ -1150,6 +1158,7 @@ static void skl_wrpll_try_divider(struct skl_wrpll_context *ctx,
ctx->p = divider;
}
+ return false;
}
static void skl_wrpll_get_multipliers(unsigned int p,
@@ -1311,13 +1320,15 @@ skl_ddi_calculate_wrpll(int clock /* in Hz */,
unsigned int p = dividers[d].list[i];
uint64_t dco_freq = p * afe_clock;
- skl_wrpll_try_divider(&ctx,
- dco_central_freq[dco],
- dco_freq,
- p);
+ if (skl_wrpll_try_divider(&ctx,
+ dco_central_freq[dco],
+ dco_freq,
+ p))
+ goto skip_remaining_dividers;
}
}
+skip_remaining_dividers:
/*
* If a solution is found with an even divider, prefer
* this one.
--
2.1.0
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