diff mbox series

[v2,2/7] drm/rockchip: dw_hdmi: Adjust cklvl & txlvl for RF/EMI

Message ID 20240908145511.3331451-3-jonas@kwiboo.se (mailing list archive)
State New
Headers show
Series rockchip: Enable 4K60Hz mode on RK3228, RK3328, RK3399 and RK356x | expand

Commit Message

Jonas Karlman Sept. 8, 2024, 2:54 p.m. UTC 
From: Yakir Yang <ykk@rock-chips.com>

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

Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
---
v2: No change
---
 drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
index 36cc700766fd..fc5e87285a91 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -202,7 +202,7 @@  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}
 };