FROMLIST: drm/rockchip: dw_hdmi: adjust cklvl & txlvl for RF/EMI

Dut to the high HDMI signal voltage driver, Mickey have meet
a serious RF/EMI problem, so we decided to reduce HDMI signal
voltage to a proper value.

The default params for phy is cklvl = 20 & txlvl = 13 (RF/EMI failed)
  ck: lvl = 13, term=100, vlo = 2.71, vhi=3.14, vswing = 0.43
  tx: lvl = 20, term=100, vlo = 2.81, vhi=3.16, vswing = 0.35

1. We decided to reduce voltage value to lower, but VSwing still
keep high, RF/EMI have been improved but still failed.
   ck: lvl =  6, term=100, vlo = 2.61, vhi=3.11, vswing = 0.50
   tx: lvl =  6, term=100, vlo = 2.61, vhi=3.11, vswing = 0.50

2. We try to keep voltage value and vswing both lower, then RF/EMI
test all passed  ;)
   ck: lvl = 11, term= 66, vlo = 2.68, vhi=3.09, vswing = 0.40
   tx: lvl = 11, term= 66, vlo = 2.68, vhi=3.09, vswing = 0.40
When we back to run HDMI different test and single-end test, we see
different test passed, but signle-end test failed. The oscilloscope
show that simgle-end clock's VL value is 1.78v (which remind LowLimit
should not lower then 2.6v).

3. That's to say there are some different between PHY document and
measure value. And according to experiment 2 results, we need to
higher clock voltage and lower data voltage, then we can keep RF/EMI
satisfied and single-end & differen test passed.
  ck: lvl =  9, term=100, vlo = 2.65, vhi=3.12, vswing = 0.47
  tx: lvl = 16, term=100, vlo = 2.75, vhi=3.15, vswing = 0.39

Change-Id: I766df9ad519ddddb9be76f95fbbdb36c5a2d6e51
Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
(am from https://patchwork.kernel.org/patch/9223303/)

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
index a621118316d8fbb475e8a5d154df555bc9ce4cb0..cdb63ac61595d3c72696684dc1d7f0355cca5e32 100644 (file)
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -124,7 +124,7 @@ static const struct dw_hdmi_curr_ctrl rockchip_cur_ctr[] = {
 static const struct dw_hdmi_phy_config rockchip_phy_config[] = {
        /*pixelclk   symbol   term   vlev*/
        { 74250000,  0x8009, 0x0004, 0x0272},
-       { 148500000, 0x802b, 0x0004, 0x028d},
+       { 165000000, 0x802b, 0x0004, 0x0209},
        { 297000000, 0x8039, 0x0005, 0x028d},
        { ~0UL,      0x0000, 0x0000, 0x0000}
 };