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From e6c76064e955ee5ce3acfce56bffbebbda8db5f6 Mon Sep 17 00:00:00 2001
From: Anthony Koo <Anthony.Koo@amd.com>
Date: Tue, 17 Apr 2018 11:40:31 -0400
Subject: [PATCH 0118/2940] drm/amd/display: Correct rounding calcs in
mod_freesync_is_valid_range
Signed-off-by: Anthony Koo <Anthony.Koo@amd.com>
Reviewed-by: Aric Cyr <Aric.Cyr@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
---
.../amd/display/modules/freesync/freesync.c | 39 ++++++++++++++++---
1 file changed, 34 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
index 349387eb9fe6..769f46777a1d 100644
--- a/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
+++ b/drivers/gpu/drm/amd/display/modules/freesync/freesync.c
@@ -887,12 +887,41 @@ bool mod_freesync_is_valid_range(struct mod_freesync *mod_freesync,
unsigned long long nominal_field_rate_in_uhz =
mod_freesync_calc_nominal_field_rate(stream);
- /* Allow for some rounding error of actual video timing by taking ceil.
- * For example, 144 Hz mode timing may actually be 143.xxx Hz when
- * calculated from pixel rate and vertical/horizontal totals, but
- * this should be allowed instead of blocking FreeSync.
+ /* Typically nominal refresh calculated can have some fractional part.
+ * Allow for some rounding error of actual video timing by taking floor
+ * of caps and request. Round the nominal refresh rate.
+ *
+ * Dividing will convert everything to units in Hz although input
+ * variable name is in uHz!
+ *
+ * Also note, this takes care of rounding error on the nominal refresh
+ * so by rounding error we only expect it to be off by a small amount,
+ * such as < 0.1 Hz. i.e. 143.9xxx or 144.1xxx.
+ *
+ * Example 1. Caps Min = 40 Hz, Max = 144 Hz
+ * Request Min = 40 Hz, Max = 144 Hz
+ * Nominal = 143.5x Hz rounded to 144 Hz
+ * This function should allow this as valid request
+ *
+ * Example 2. Caps Min = 40 Hz, Max = 144 Hz
+ * Request Min = 40 Hz, Max = 144 Hz
+ * Nominal = 144.4x Hz rounded to 144 Hz
+ * This function should allow this as valid request
+ *
+ * Example 3. Caps Min = 40 Hz, Max = 144 Hz
+ * Request Min = 40 Hz, Max = 144 Hz
+ * Nominal = 120.xx Hz rounded to 120 Hz
+ * This function should return NOT valid since the requested
+ * max is greater than current timing's nominal
+ *
+ * Example 4. Caps Min = 40 Hz, Max = 120 Hz
+ * Request Min = 40 Hz, Max = 120 Hz
+ * Nominal = 144.xx Hz rounded to 144 Hz
+ * This function should return NOT valid since the nominal
+ * is greater than the capability's max refresh
*/
- nominal_field_rate_in_uhz = div_u64(nominal_field_rate_in_uhz, 1000000);
+ nominal_field_rate_in_uhz =
+ div_u64(nominal_field_rate_in_uhz + 500000, 1000000);
min_refresh_cap_in_uhz /= 1000000;
max_refresh_cap_in_uhz /= 1000000;
min_refresh_request_in_uhz /= 1000000;
--
2.17.1
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