linux-kernel - [PATCH v5 14/24] drm/msm/dsi/phy: Toggle back buffer resync after preparing PLL

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Message-Id: <20250430-b4-sm8750-display-v5-14-8cab30c3e4df@linaro.org>
Date: Wed, 30 Apr 2025 15:00:44 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Krishna Manikandan <quic_mkrishn@...cinc.com>, 
 Jonathan Marek <jonathan@...ek.ca>, Kuogee Hsieh <quic_khsieh@...cinc.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, 
 Dmitry Baryshkov <lumag@...nel.org>, Rob Clark <robdclark@...il.com>, 
 Bjorn Andersson <andersson@...nel.org>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>, 
 Rob Clark <robdclark@...omium.org>, linux-clk@...r.kernel.org, 
 Srinivas Kandagatla <srini@...nel.org>
Subject: [PATCH v5 14/24] drm/msm/dsi/phy: Toggle back buffer resync after
 preparing PLL

According to Hardware Programming Guide for DSI PHY, the retime buffer
resync should be done after PLL clock users (byte_clk and intf_byte_clk)
are enabled.  Downstream also does it as part of configuring the PLL.

Driver was only turning of the resync FIFO buffer, but never bringing it
on again.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

---

Changes in v5:
1. New patch
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
index a92decbee5b5433853ed973747f7705d9079068d..ca1a120f630a3650bf6d9f9d426cccea88c22e7f 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -467,6 +467,10 @@ static int dsi_pll_7nm_vco_prepare(struct clk_hw *hw)
 	if (pll_7nm->slave)
 		dsi_pll_enable_global_clk(pll_7nm->slave);
 
+	writel(0x1, pll_7nm->phy->base + REG_DSI_7nm_PHY_CMN_RBUF_CTRL);
+	if (pll_7nm->slave)
+		writel(0x1, pll_7nm->slave->phy->base + REG_DSI_7nm_PHY_CMN_RBUF_CTRL);
+
 error:
 	return rc;
 }

-- 
2.45.2