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From:   Claudiu <claudiu.beznea@tuxon.dev>
To:     geert+renesas@glider.be, mturquette@baylibre.com, sboyd@kernel.org,
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        biju.das.jz@bp.renesas.com, quic_bjorande@quicinc.com,
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Cc:     linux-renesas-soc@vger.kernel.org, linux-clk@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-mmc@vger.kernel.org, linux-gpio@vger.kernel.org,
        linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Subject: [PATCH 07/37] clk: renesas: rzg2l: lock around writes to mux register
Date:   Tue, 12 Sep 2023 07:51:27 +0300
Message-Id: <20230912045157.177966-8-claudiu.beznea.uj@bp.renesas.com>
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From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>

SD MUX output (SD0) is further divided by 4 in G2{L, UL}. The divided
clock is SD0_DIV4. SD0_DIV4 is registered with CLK_SET_RATE_PARENT which
means a rate request for it is propagated to the MUX and could reach
rzg2l_cpg_sd_clk_mux_set_parent() concurrently with the users of SD0.
Add proper locking to avoid concurrent access on SD MUX set rate
registers.

Fixes: eaff33646f4cb ("clk: renesas: rzg2l: Add SDHI clk mux support")
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
---
 drivers/clk/renesas/rzg2l-cpg.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/clk/renesas/rzg2l-cpg.c b/drivers/clk/renesas/rzg2l-cpg.c
index 70d1c28ba088..1195d4b1f545 100644
--- a/drivers/clk/renesas/rzg2l-cpg.c
+++ b/drivers/clk/renesas/rzg2l-cpg.c
@@ -189,6 +189,7 @@ static int rzg2l_cpg_sd_clk_mux_set_parent(struct clk_hw *hw, u8 index)
 	u32 shift = GET_SHIFT(hwdata->conf);
 	const u32 clk_src_266 = 2;
 	u32 msk, val, bitmask;
+	unsigned long flags;
 	int ret;
 
 	/*
@@ -203,25 +204,27 @@ static int rzg2l_cpg_sd_clk_mux_set_parent(struct clk_hw *hw, u8 index)
 	 * the index to value mapping is done by adding 1 to the index.
 	 */
 	bitmask = (GENMASK(GET_WIDTH(hwdata->conf) - 1, 0) << shift) << 16;
+	spin_lock_irqsave(&priv->rmw_lock, flags);
 	if (index != clk_src_266) {
 		writel(bitmask | ((clk_src_266 + 1) << shift), priv->base + off);
 
 		msk = off ? CPG_CLKSTATUS_SELSDHI1_STS : CPG_CLKSTATUS_SELSDHI0_STS;
 
-		ret = readl_poll_timeout(priv->base + CPG_CLKSTATUS, val,
-					 !(val & msk), 100,
-					 CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US);
-		if (ret) {
-			dev_err(priv->dev, "failed to switch clk source\n");
-			return ret;
-		}
+		ret = readl_poll_timeout_atomic(priv->base + CPG_CLKSTATUS, val,
+						!(val & msk), 100,
+						CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US);
+		if (ret)
+			goto unlock;
 	}
 
 	writel(bitmask | ((index + 1) << shift), priv->base + off);
 
-	ret = readl_poll_timeout(priv->base + CPG_CLKSTATUS, val,
-				 !(val & msk), 100,
-				 CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US);
+	ret = readl_poll_timeout_atomic(priv->base + CPG_CLKSTATUS, val,
+					!(val & msk), 100,
+					CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US);
+unlock:
+	spin_unlock_irqrestore(&priv->rmw_lock, flags);
+
 	if (ret)
 		dev_err(priv->dev, "failed to switch clk source\n");
 
-- 
2.39.2