drm/i915: clean up dsi pll calculation

Improve readability. No functional changes.

v2: use more rational types (Ville)

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
index 3622d0b..cfd5277 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dsi_pll.c
+++ b/drivers/gpu/drm/i915/intel_dsi_pll.c
@@ -162,53 +162,34 @@ static u32 dsi_clk_from_pclk(u32 pclk, int pixel_format, int lane_count)
 
 #endif
 
-static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
+static int dsi_calc_mnp(int target_dsi_clk, struct dsi_mnp *dsi_mnp)
 {
-       u32 m, n, p;
-       u32 ref_clk;
-       u32 error;
-       u32 tmp_error;
-       int target_dsi_clk;
-       int calc_dsi_clk;
-       u32 calc_m;
-       u32 calc_p;
+       unsigned int calc_m = 0, calc_p = 0;
+       unsigned int m, n, p;
+       int ref_clk = 25000;
+       int delta = target_dsi_clk;
        u32 m_seed;
 
-       /* dsi_clk is expected in KHZ */
-       if (dsi_clk < 300000 || dsi_clk > 1150000) {
+       /* target_dsi_clk is expected in kHz */
+       if (target_dsi_clk < 300000 || target_dsi_clk > 1150000) {
                DRM_ERROR("DSI CLK Out of Range\n");
                return -ECHRNG;
        }
 
-       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) {
-                               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;
+       for (m = 62; m <= 92 && delta; m++) {
+               for (p = 2; p <= 6 && delta; p++) {
+                       /*
+                        * Find the optimal m and p divisors with minimal delta
+                        * +/- the required clock
+                        */
+                       int calc_dsi_clk = (m * ref_clk) / p;
+                       int d = abs(target_dsi_clk - calc_dsi_clk);
+                       if (d < delta) {
+                               delta = d;
                                calc_m = m;
                                calc_p = p;
                        }
                }
-
-               if (error == 0)
-                       break;
        }
 
        m_seed = lfsr_converts[calc_m - 62];