Commit bf2af91c authored by Anthony Koo's avatar Anthony Koo Committed by Alex Deucher
Browse files

drm/amd/display: Correct rounding calcs in mod_freesync_is_valid_range 



Signed-off-by: default avatarAnthony Koo <Anthony.Koo@amd.com>
Reviewed-by: default avatarAric Cyr <Aric.Cyr@amd.com>
Acked-by: default avatarHarry Wentland <harry.wentland@amd.com>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 953c2901

drivers/gpu/drm/amd/display/modules/freesync/freesync.c

+34 −5
Original line number Diff line number Diff line
@@ -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;