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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>
This commit is contained in:
Jani Nikula 2015-05-12 15:23:09 +03:00 committed by Daniel Vetter
parent 6364e67e4a
commit 7471bf4e0e
1 changed files with 17 additions and 36 deletions
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53
drivers/gpu/drm/i915/intel_dsi_pll.c
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@ -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];