Message-Id: <20251027-topic-sm8x50-fix-dsi-bonded-v1-1-a477cd3f907d@linaro.org>
Date: Mon, 27 Oct 2025 14:09:48 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Rob Clark <robin.clark@....qualcomm.com>, 
 Dmitry Baryshkov <lumag@...nel.org>, 
 Abhinav Kumar <abhinav.kumar@...ux.dev>, 
 Jessica Zhang <jessica.zhang@....qualcomm.com>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
 linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Neil Armstrong <neil.armstrong@...aro.org>
Subject: [PATCH] drm/msm: dsi: fix PLL init in bonded mode

When in bonded DSI mode, only one PLL in one DSI PHY is used for both
DSI PHYs, meaning that parents of the secondary DSI PHY will use the
primary DSI PHY PLL as parent.

In this case the primary DSI PHY PLL will be set even if the primary
DSI PHY is not yet enabled. The DSI PHY code has support for this
particular use-case and will handle the fact the PLL was already
set when initializing the primary DSI PHY.

By introducing a protected variable pll_enable_cnt in the commit
cb55f39bf7b1 ("drm/msm/dsi/phy: Fix reading zero as PLL rates when unprepared"),
this variable is only initially set to 1 when the DSI PHY is initialized
making it impossible to set the PLL before, breaking the bonded DSI
use case by returning 0 when setting the PLL from the secondary DSI
PHY driver and skipping the correct clocks initialization.

But since it was already possible to set the PLL without enabling
the DSI PHY, just drop the pll_enable_cnt setting from the PHY
enable/disable and simply increment/decrement the pll_enable_cnt
variable from the dsi_pll_enable/disable_pll_bias to make sure any
PLL operation is done with the PLL BIAS enabled.

Fixes: cb55f39bf7b1 ("drm/msm/dsi/phy: Fix reading zero as PLL rates when unprepared")
Closes: https://lore.kernel.org/all/50a49d72-2b1e-471d-b0c4-d5a0b38b2a21@linaro.org/
Tested-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy.h     |  1 -
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 18 ++----------------
 2 files changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h
index e391505fdaf0..3cbf08231492 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy.h
@@ -109,7 +109,6 @@ struct msm_dsi_phy {
 	struct msm_dsi_dphy_timing timing;
 	const struct msm_dsi_phy_cfg *cfg;
 	void *tuning_cfg;
-	void *pll_data;
 
 	enum msm_dsi_phy_usecase usecase;
 	bool regulator_ldo_mode;
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 32f06edd21a9..c5e1d2016bcc 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -426,11 +426,8 @@ static void dsi_pll_enable_pll_bias(struct dsi_pll_7nm *pll)
 	u32 data;
 
 	spin_lock_irqsave(&pll->pll_enable_lock, flags);
-	if (pll->pll_enable_cnt++) {
-		spin_unlock_irqrestore(&pll->pll_enable_lock, flags);
-		WARN_ON(pll->pll_enable_cnt == INT_MAX);
-		return;
-	}
+	pll->pll_enable_cnt++;
+	WARN_ON(pll->pll_enable_cnt == INT_MAX);
 
 	data = readl(pll->phy->base + REG_DSI_7nm_PHY_CMN_CTRL_0);
 	data |= DSI_7nm_PHY_CMN_CTRL_0_PLL_SHUTDOWNB;
@@ -876,7 +873,6 @@ static int dsi_pll_7nm_init(struct msm_dsi_phy *phy)
 	spin_lock_init(&pll_7nm->pll_enable_lock);
 
 	pll_7nm->phy = phy;
-	phy->pll_data = pll_7nm;
 
 	ret = pll_7nm_register(pll_7nm, phy->provided_clocks->hws);
 	if (ret) {
@@ -965,10 +961,8 @@ static int dsi_7nm_phy_enable(struct msm_dsi_phy *phy,
 	u32 const delay_us = 5;
 	u32 const timeout_us = 1000;
 	struct msm_dsi_dphy_timing *timing = &phy->timing;
-	struct dsi_pll_7nm *pll = phy->pll_data;
 	void __iomem *base = phy->base;
 	bool less_than_1500_mhz;
-	unsigned long flags;
 	u32 vreg_ctrl_0, vreg_ctrl_1, lane_ctrl0;
 	u32 glbl_pemph_ctrl_0;
 	u32 glbl_str_swi_cal_sel_ctrl, glbl_hstx_str_ctrl_0;
@@ -1090,13 +1084,10 @@ static int dsi_7nm_phy_enable(struct msm_dsi_phy *phy,
 		glbl_rescode_bot_ctrl = 0x3c;
 	}
 
-	spin_lock_irqsave(&pll->pll_enable_lock, flags);
-	pll->pll_enable_cnt = 1;
 	/* de-assert digital and pll power down */
 	data = DSI_7nm_PHY_CMN_CTRL_0_DIGTOP_PWRDN_B |
 	       DSI_7nm_PHY_CMN_CTRL_0_PLL_SHUTDOWNB;
 	writel(data, base + REG_DSI_7nm_PHY_CMN_CTRL_0);
-	spin_unlock_irqrestore(&pll->pll_enable_lock, flags);
 
 	/* Assert PLL core reset */
 	writel(0x00, base + REG_DSI_7nm_PHY_CMN_PLL_CNTRL);
@@ -1209,9 +1200,7 @@ static bool dsi_7nm_set_continuous_clock(struct msm_dsi_phy *phy, bool enable)
 
 static void dsi_7nm_phy_disable(struct msm_dsi_phy *phy)
 {
-	struct dsi_pll_7nm *pll = phy->pll_data;
 	void __iomem *base = phy->base;
-	unsigned long flags;
 	u32 data;
 
 	DBG("");
@@ -1238,11 +1227,8 @@ static void dsi_7nm_phy_disable(struct msm_dsi_phy *phy)
 	writel(data, base + REG_DSI_7nm_PHY_CMN_CTRL_0);
 	writel(0, base + REG_DSI_7nm_PHY_CMN_LANE_CTRL0);
 
-	spin_lock_irqsave(&pll->pll_enable_lock, flags);
-	pll->pll_enable_cnt = 0;
 	/* Turn off all PHY blocks */
 	writel(0x00, base + REG_DSI_7nm_PHY_CMN_CTRL_0);
-	spin_unlock_irqrestore(&pll->pll_enable_lock, flags);
 
 	/* make sure phy is turned off */
 	wmb();

---
base-commit: dcb6fa37fd7bc9c3d2b066329b0d27dedf8becaa
change-id: 20251027-topic-sm8x50-fix-dsi-bonded-c88f880aca0a

Best regards,
-- 
Neil Armstrong <neil.armstrong@...aro.org>

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