clk: renesas: rzg2l: Lock around writes to mux register

The 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 accesses on SD MUX set rate
registers.

Fixes: eaff336 ("clk: renesas: rzg2l: Add SDHI clk mux support")
Signed-off-by: Claudiu Beznea <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Geert Uytterhoeven <[email protected]>

Author: claudiubeznea

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;
 
 	/*
@@ -204,23 +205,25 @@ static int rzg2l_cpg_sd_clk_mux_set_parent(struct clk_hw *hw, u8 index)
 	 */
 	bitmask = (GENMASK(GET_WIDTH(hwdata->conf) - 1, 0) << shift) << 16;
 	msk = off ? CPG_CLKSTATUS_SELSDHI1_STS : CPG_CLKSTATUS_SELSDHI0_STS;
+	spin_lock_irqsave(&priv->rmw_lock, flags);
 	if (index != clk_src_266) {
 		writel(bitmask | ((clk_src_266 + 1) << shift), priv->base + off);
 
-		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), 10,
+						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), 10,
+					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");
 

drivers/clk/renesas/rzg2l-cpg.h

@@ -43,7 +43,7 @@
 #define CPG_CLKSTATUS_SELSDHI0_STS	BIT(28)
 #define CPG_CLKSTATUS_SELSDHI1_STS	BIT(29)
 
-#define CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US	20000
+#define CPG_SDHI_CLK_SWITCH_STATUS_TIMEOUT_US	200
 
 /* n = 0/1/2 for PLL1/4/6 */
 #define CPG_SAMPLL_CLK1(n)	(0x04 + (16 * n))