mailbox: stm32_ipcc: add spinlock to fix channels concurrent access

Add spinlock protection on IPCC register update to avoid race condition.
Without this fix, stm32_ipcc_set_bits and stm32_ipcc_clr_bits can be
called in parallel for different channels. This results in register
corruptions.
Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Reviewed-by: Fabien Dessenne <fabien.dessenne@st.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/stm32-ipcc.c

@@ -50,6 +50,7 @@ struct stm32_ipcc {
 	void __iomem *reg_base;
 	void __iomem *reg_proc;
 	struct clk *clk;
+	spinlock_t lock; /* protect access to IPCC registers */
 	int irqs[IPCC_IRQ_NUM];
 	int wkp;
 	u32 proc_id;
@@ -58,14 +59,24 @@ struct stm32_ipcc {
 	u32 xmr;
 };
 
-static inline void stm32_ipcc_set_bits(void __iomem *reg, u32 mask)
+static inline void stm32_ipcc_set_bits(spinlock_t *lock, void __iomem *reg,
+				       u32 mask)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(lock, flags);
 	writel_relaxed(readl_relaxed(reg) | mask, reg);
+	spin_unlock_irqrestore(lock, flags);
 }
 
-static inline void stm32_ipcc_clr_bits(void __iomem *reg, u32 mask)
+static inline void stm32_ipcc_clr_bits(spinlock_t *lock, void __iomem *reg,
+				       u32 mask)
 {
+	unsigned long flags;
+
+	spin_lock_irqsave(lock, flags);
 	writel_relaxed(readl_relaxed(reg) & ~mask, reg);
+	spin_unlock_irqrestore(lock, flags);
 }
 
 static irqreturn_t stm32_ipcc_rx_irq(int irq, void *data)
@@ -92,7 +103,7 @@ static irqreturn_t stm32_ipcc_rx_irq(int irq, void *data)
 
 		mbox_chan_received_data(&ipcc->controller.chans[chan], NULL);
 
-		stm32_ipcc_set_bits(ipcc->reg_proc + IPCC_XSCR,
+		stm32_ipcc_set_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XSCR,
 				    RX_BIT_CHAN(chan));
 
 		ret = IRQ_HANDLED;
@@ -121,7 +132,7 @@ static irqreturn_t stm32_ipcc_tx_irq(int irq, void *data)
 		dev_dbg(dev, "%s: chan:%d tx\n", __func__, chan);
 
 		/* mask 'tx channel free' interrupt */
-		stm32_ipcc_set_bits(ipcc->reg_proc + IPCC_XMR,
+		stm32_ipcc_set_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XMR,
 				    TX_BIT_CHAN(chan));
 
 		mbox_chan_txdone(&ipcc->controller.chans[chan], 0);
@@ -141,10 +152,12 @@ static int stm32_ipcc_send_data(struct mbox_chan *link, void *data)
 	dev_dbg(ipcc->controller.dev, "%s: chan:%d\n", __func__, chan);
 
 	/* set channel n occupied */
-	stm32_ipcc_set_bits(ipcc->reg_proc + IPCC_XSCR, TX_BIT_CHAN(chan));
+	stm32_ipcc_set_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XSCR,
+			    TX_BIT_CHAN(chan));
 
 	/* unmask 'tx channel free' interrupt */
-	stm32_ipcc_clr_bits(ipcc->reg_proc + IPCC_XMR, TX_BIT_CHAN(chan));
+	stm32_ipcc_clr_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XMR,
+			    TX_BIT_CHAN(chan));
 
 	return 0;
 }
@@ -163,7 +176,8 @@ static int stm32_ipcc_startup(struct mbox_chan *link)
 	}
 
 	/* unmask 'rx channel occupied' interrupt */
-	stm32_ipcc_clr_bits(ipcc->reg_proc + IPCC_XMR, RX_BIT_CHAN(chan));
+	stm32_ipcc_clr_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XMR,
+			    RX_BIT_CHAN(chan));
 
 	return 0;
 }
@@ -175,7 +189,7 @@ static void stm32_ipcc_shutdown(struct mbox_chan *link)
 					       controller);
 
 	/* mask rx/tx interrupt */
-	stm32_ipcc_set_bits(ipcc->reg_proc + IPCC_XMR,
+	stm32_ipcc_set_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XMR,
 			    RX_BIT_CHAN(chan) | TX_BIT_CHAN(chan));
 
 	clk_disable_unprepare(ipcc->clk);
@@ -208,6 +222,8 @@ static int stm32_ipcc_probe(struct platform_device *pdev)
 	if (!ipcc)
 		return -ENOMEM;
 
+	spin_lock_init(&ipcc->lock);
+
 	/* proc_id */
 	if (of_property_read_u32(np, "st,proc-id", &ipcc->proc_id)) {
 		dev_err(dev, "Missing st,proc-id\n");
@@ -259,9 +275,10 @@ static int stm32_ipcc_probe(struct platform_device *pdev)
 	}
 
 	/* mask and enable rx/tx irq */
-	stm32_ipcc_set_bits(ipcc->reg_proc + IPCC_XMR,
+	stm32_ipcc_set_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XMR,
 			    RX_BIT_MASK | TX_BIT_MASK);
-	stm32_ipcc_set_bits(ipcc->reg_proc + IPCC_XCR, XCR_RXOIE | XCR_TXOIE);
+	stm32_ipcc_set_bits(&ipcc->lock, ipcc->reg_proc + IPCC_XCR,
+			    XCR_RXOIE | XCR_TXOIE);
 
 	/* wakeup */
 	if (of_property_read_bool(np, "wakeup-source")) {