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Commit 8e1eed5a authored by Shobhit Kumar's avatar Shobhit Kumar Committed by Daniel Vetter
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drm/i915: Try harder to get best m, n, p values with minimal error 



Basically check for both +ive and -ive deviation from target clock and
pick the one with minimal error. If we get a direct match, break from
loop to acheive some optimization.

v2: Use signed variable for target and calculated dsi clock values

Signed-off-by: default avatarVijayakumar Balakrishnan <vijayakumar.balakrishnan@intel.com>
Signed-off-by: default avatarShobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: default avatarJani Nikula <jani.nikula@intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 44d4c6ee

drivers/gpu/drm/i915/intel_dsi_pll.c

+20 −10
Original line number Original line Diff line number Diff line
@@ -169,8 +169,8 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp) 
	u32 ref_clk;

	u32 ref_clk;

	u32 error;

	u32 error;

	u32 tmp_error;

	u32 tmp_error;

	u32 target_dsi_clk;

	int target_dsi_clk;

	u32 calc_dsi_clk;

	int calc_dsi_clk;

	u32 calc_m;

	u32 calc_m;

	u32 calc_p;

	u32 calc_p;

	u32 m_seed;

	u32 m_seed;
@@ -184,22 +184,32 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp) 
	ref_clk = 25000;

	ref_clk = 25000;

	target_dsi_clk = dsi_clk;

	target_dsi_clk = dsi_clk;

	error = 0xFFFFFFFF;

	error = 0xFFFFFFFF;

	tmp_error = 0xFFFFFFFF;

	calc_m = 0;

	calc_m = 0;

	calc_p = 0;

	calc_p = 0;





	for (m = 62; m <= 92; m++) {

	for (m = 62; m <= 92; m++) {

		for (p = 2; p <= 6; p++) {

		for (p = 2; p <= 6; p++) {



			/* Find the optimal m and p divisors

			with minimal error +/- the required clock */

			calc_dsi_clk = (m * ref_clk) / p;

			calc_dsi_clk = (m * ref_clk) / p;

			if (calc_dsi_clk >= target_dsi_clk) {

			if (calc_dsi_clk == target_dsi_clk) {

				tmp_error = calc_dsi_clk - target_dsi_clk;

				calc_m = m;

				calc_p = p;

				error = 0;

				break;

			} else

				tmp_error = abs(target_dsi_clk - calc_dsi_clk);



			if (tmp_error < error) {

			if (tmp_error < error) {

				error = tmp_error;

				error = tmp_error;

				calc_m = m;

				calc_m = m;

				calc_p = p;

				calc_p = p;

			}

			}

		}

		}

		}



		if (error == 0)

			break;

	}

	}





	m_seed = lfsr_converts[calc_m - 62];

	m_seed = lfsr_converts[calc_m - 62];