linux-kernel - [PATCH 02/12] phy: rockchip: samsung-hdptx: Reduce ROPLL loop bandwidth

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Message-Id: <20250708-phy-hdptx-frl-v1-2-cfe096e224f4@collabora.com>
Date: Tue, 08 Jul 2025 22:35:43 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Vinod Koul <vkoul@...nel.org>, 
 Kishon Vijay Abraham I <kishon@...nel.org>, 
 Heiko Stuebner <heiko@...ech.de>, Algea Cao <algea.cao@...k-chips.com>
Cc: kernel@...labora.com, linux-phy@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 linux-rockchip@...ts.infradead.org
Subject: [PATCH 02/12] phy: rockchip: samsung-hdptx: Reduce ROPLL loop
 bandwidth

Due to its relatively low frequency, a noise stemming from the 24MHz PLL
reference clock may traverse the low-pass loop filter of ROPLL, which
could potentially generate some HDMI flash artifacts.

Reduce ROPLL loop bandwidth in an attempt to mitigate the problem.

Fixes: 553be2830c5f ("phy: rockchip: Add Samsung HDMI/eDP Combo PHY driver")
Co-developed-by: Algea Cao <algea.cao@...k-chips.com>
Signed-off-by: Algea Cao <algea.cao@...k-chips.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
---
 drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
index 79db57ee90d1487b51f4ddadde870a275dd7b17b..d7d6c1ebacc890e257c1550210ee144387ef7183 100644
--- a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
+++ b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
@@ -500,9 +500,7 @@ static const struct reg_sequence rk_hdtpx_common_cmn_init_seq[] = {
 	REG_SEQ0(CMN_REG(0043), 0x00),
 	REG_SEQ0(CMN_REG(0044), 0x46),
 	REG_SEQ0(CMN_REG(0045), 0x24),
-	REG_SEQ0(CMN_REG(0046), 0xff),
 	REG_SEQ0(CMN_REG(0047), 0x00),
-	REG_SEQ0(CMN_REG(0048), 0x44),
 	REG_SEQ0(CMN_REG(0049), 0xfa),
 	REG_SEQ0(CMN_REG(004a), 0x08),
 	REG_SEQ0(CMN_REG(004b), 0x00),
@@ -575,6 +573,8 @@ static const struct reg_sequence rk_hdtpx_tmds_cmn_init_seq[] = {
 	REG_SEQ0(CMN_REG(0034), 0x00),
 	REG_SEQ0(CMN_REG(003d), 0x40),
 	REG_SEQ0(CMN_REG(0042), 0x78),
+	REG_SEQ0(CMN_REG(0046), 0xdd),
+	REG_SEQ0(CMN_REG(0048), 0x11),
 	REG_SEQ0(CMN_REG(004e), 0x34),
 	REG_SEQ0(CMN_REG(005c), 0x25),
 	REG_SEQ0(CMN_REG(005e), 0x4f),

-- 
2.50.0