[PATCH 3/4] drm/i915: Compute dsi_clk from pixel clock

Shobhit Kumar
2013-10-21T12:14:09Z

Minor modification to m_n_p calculations as well

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
---
drivers/gpu/drm/i915/intel_dsi_pll.c | 75 ++++++++++++++++++++++++++++------
1 file changed, 63 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dsi_pll.c b/drivers/gpu/drm/i915/intel_dsi_pll.c
index 44279b2..bf12335 100644
--- a/drivers/gpu/drm/i915/intel_dsi_pll.c
+++ b/drivers/gpu/drm/i915/intel_dsi_pll.c
@@ -50,6 +50,8 @@ static const u32 lfsr_converts[] = {
71, 35 /* 91 - 92 */
};

+#ifdef DSI_CLK_FROM_RR
+
static u32 dsi_rr_formula(const struct drm_display_mode *mode,
int pixel_format, int video_mode_format,
int lane_count, bool eotp)
@@ -129,6 +131,40 @@ static u32 dsi_rr_formula(const struct drm_display_mode *mode,
return dsi_clk;
}

+#else
+
+/* Get DSI clock from pixel clock */
+static u32 dsi_clk_from_pclk(const struct drm_display_mode *mode,
+ int pixel_format, int lane_count)
+{
+ u32 dsi_bit_clock_hz, dsi_clk;
+ u32 bpp;
+
+ switch (pixel_format) {
+ default:
+ case VID_MODE_FORMAT_RGB888:
+ case VID_MODE_FORMAT_RGB666_LOOSE:
+ bpp = 24;
+ break;
+ case VID_MODE_FORMAT_RGB666:
+ bpp = 18;
+ break;
+ case VID_MODE_FORMAT_RGB565:
+ bpp = 16;
+ break;
+ }
+
+ /* DSI data rate = pixel clock * bits per pixel / lane count
+ pixel clock is converted from KHz to Hz */
+ dsi_bit_clock_hz = (((mode->clock * 1000) * bpp) / lane_count);
+
+ /* DSI clock rate */
+ dsi_clk = dsi_bit_clock_hz / (1000 * 1000);
+ return dsi_clk;
+}
+
+#endif
+
#ifdef MNP_FROM_TABLE

struct dsi_clock_table {
@@ -208,29 +244,42 @@ static int dsi_calc_mnp(u32 dsi_clk, struct dsi_mnp *dsi_mnp)
ref_clk = 25000;
target_dsi_clk = dsi_clk * 1000;
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) {
+ if (calc_dsi_clk == target_dsi_clk) {
+ calc_m = m;
+ calc_p = p;
+ error = 0;
+ break;
+ } else 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;
- }
+ else
+ tmp_error = 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];
n = 1;
+
dsi_mnp->dsi_pll_ctrl = 1 << (DSI_PLL_P1_POST_DIV_SHIFT + calc_p - 2);
dsi_mnp->dsi_pll_div = (n - 1) << DSI_PLL_N1_DIV_SHIFT |
- m_seed << DSI_PLL_M1_DIV_SHIFT;
+ m_seed << DSI_PLL_M1_DIV_SHIFT;

return 0;
}
@@ -249,11 +298,13 @@ static void vlv_configure_dsi_pll(struct intel_encoder *encoder)
struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
int ret;
struct dsi_mnp dsi_mnp;
- u32 dsi_clk;
+ u32 dsi_clk = 0;

- dsi_clk = dsi_rr_formula(mode, intel_dsi->pixel_format,
- intel_dsi->video_mode_format,
- intel_dsi->lane_count, !intel_dsi->eot_disable);
+ if (intel_dsi->dsi_clock_freq)
+ dsi_clk = intel_dsi->dsi_clock_freq;
+ else
+ dsi_clk = dsi_clk_from_pclk(mode, intel_dsi->pixel_format,
+ intel_dsi->lane_count);

ret = dsi_calc_mnp(dsi_clk, &dsi_mnp);
if (ret) {
--
1.7.9.5