From 8e1eed5aa8fe6cdd2c445b7aded42498523ad4dd Mon Sep 17 00:00:00 2001 From: Shobhit Kumar Date: Tue, 10 Dec 2013 12:14:57 +0530 Subject: [PATCH] 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: Vijayakumar Balakrishnan Signed-off-by: Shobhit Kumar Reviewed-by: Jani Nikula Signed-off-by: Daniel Vetter --- drivers/gpu/drm/i915/intel_dsi_pll.c | 30 ++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c index 0d1b17fee018..ba79ec19da3b 100644 --- a/drivers/gpu/drm/i915/intel_dsi_pll.c +++ b/drivers/gpu/drm/i915/intel_dsi_pll.c @@ -169,8 +169,8 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp) u32 ref_clk; u32 error; u32 tmp_error; - u32 target_dsi_clk; - u32 calc_dsi_clk; + int target_dsi_clk; + int calc_dsi_clk; u32 calc_m; u32 calc_p; u32 m_seed; @@ -184,22 +184,32 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp) ref_clk = 25000; target_dsi_clk = dsi_clk; error = 0xFFFFFFFF; + tmp_error = 0xFFFFFFFF; calc_m = 0; calc_p = 0; for (m = 62; m <= 92; m++) { 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; - if (calc_dsi_clk >= target_dsi_clk) { - tmp_error = calc_dsi_clk - target_dsi_clk; - if (tmp_error < error) { - error = tmp_error; - calc_m = m; - calc_p = p; - } + if (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) { + error = tmp_error; + calc_m = m; + calc_p = p; } } + + if (error == 0) + break; } m_seed = lfsr_converts[calc_m - 62]; -- 2.20.1