linux-kernel - [PATCH 1/3] drm/msm/dsi/phy: Protect PHY_CMN_CLK

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Message-Id: <20250131-drm-msm-phy-pll-cfg-reg-v1-1-3b99efeb2e8d@linaro.org>
Date: Fri, 31 Jan 2025 16:02:50 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Rob Clark <robdclark@...il.com>, 
 Abhinav Kumar <quic_abhinavk@...cinc.com>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: [PATCH 1/3] drm/msm/dsi/phy: Protect PHY_CMN_CLK_CFG0 updated from
 driver side

PHY_CMN_CLK_CFG0 register is updated by the PHY driver and by two
divider clocks from Common Clock Framework:
devm_clk_hw_register_divider_parent_hw().  Concurrent access by the
clocks side is protected with spinlock, however driver's side in
restoring state is not.  Restoring state is called from
msm_dsi_phy_enable(), so there could be a path leading to concurrent and
conflicting updates with clock framework.

Add missing lock usage on the PHY driver side, encapsulated in its own
function so the code will be still readable.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---
 drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

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 031446c87daec0af3f81df324158311f5a80014e..c164f845653816291ad96c863257f75462ef58e7 100644
--- a/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
+++ b/drivers/gpu/drm/msm/dsi/phy/dsi_phy_7nm.c
@@ -372,6 +372,15 @@ static void dsi_pll_enable_pll_bias(struct dsi_pll_7nm *pll)
 	ndelay(250);
 }
 
+static void dsi_pll_cmn_clk_cfg0_write(struct dsi_pll_7nm *pll, u32 val)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&pll->postdiv_lock, flags);
+	writel(val, pll->phy->base + REG_DSI_7nm_PHY_CMN_CLK_CFG0);
+	spin_unlock_irqrestore(&pll->postdiv_lock, flags);
+}
+
 static void dsi_pll_disable_global_clk(struct dsi_pll_7nm *pll)
 {
 	u32 data;
@@ -574,8 +583,8 @@ static int dsi_7nm_pll_restore_state(struct msm_dsi_phy *phy)
 	val |= cached->pll_out_div;
 	writel(val, pll_7nm->phy->pll_base + REG_DSI_7nm_PHY_PLL_PLL_OUTDIV_RATE);
 
-	writel(cached->bit_clk_div | (cached->pix_clk_div << 4),
-	       phy_base + REG_DSI_7nm_PHY_CMN_CLK_CFG0);
+	dsi_pll_cmn_clk_cfg0_write(pll_7nm,
+				   cached->bit_clk_div | (cached->pix_clk_div << 4));
 
 	val = readl(phy_base + REG_DSI_7nm_PHY_CMN_CLK_CFG1);
 	val &= ~0x3;

-- 
2.43.0