From 6e94e2871eb706a17692acf7ef85ecf2789f6433 Mon Sep 17 00:00:00 2001
From: Yakir Yang <ykk@rock-chips.com>
Date: Sun, 8 Sep 2024 14:54:59 +0000
Subject: [PATCH] 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

Signed-off-by: Yakir Yang <ykk@rock-chips.com>
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240908145511.3331451-3-jonas@kwiboo.se
---
 drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 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 ro
 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}
 };
