fsi: Aspeed: Add mutex to protect HW access

There is nothing to prevent multiple commands being executed
simultaneously. Add a mutex to prevent this.

Fixes: 606397d6 ("fsi: Add ast2600 master driver")
Reviewed-by: NJoel Stanley <joel@jms.id.au>
Reviewed-by: NMilton Miller <miltonm@us.ibm.com>
Signed-off-by: NEddie James <eajames@linux.ibm.com>
Signed-off-by: NJoel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20201120004929.185239-1-joel@jms.id.auSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/fsi/fsi-master-aspeed.c

@@ -8,6 +8,7 @@
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
@@ -19,6 +20,7 @@
 
 struct fsi_master_aspeed {
 	struct fsi_master	master;
+	struct mutex		lock;	/* protect HW access */
 	struct device		*dev;
 	void __iomem		*base;
 	struct clk		*clk;
@@ -254,6 +256,8 @@ static int aspeed_master_read(struct fsi_master *master, int link,
 	addr |= id << 21;
 	addr += link * FSI_HUB_LINK_SIZE;
 
+	mutex_lock(&aspeed->lock);
+
 	switch (size) {
 	case 1:
 		ret = opb_readb(aspeed, fsi_base + addr, val);
@@ -265,14 +269,14 @@ static int aspeed_master_read(struct fsi_master *master, int link,
 		ret = opb_readl(aspeed, fsi_base + addr, val);
 		break;
 	default:
-		return -EINVAL;
+		ret = -EINVAL;
+		goto done;
 	}
 
 	ret = check_errors(aspeed, ret);
-	if (ret)
+done:
+	mutex_unlock(&aspeed->lock);
 	return ret;
-
-	return 0;
 }
 
 static int aspeed_master_write(struct fsi_master *master, int link,
@@ -287,6 +291,8 @@ static int aspeed_master_write(struct fsi_master *master, int link,
 	addr |= id << 21;
 	addr += link * FSI_HUB_LINK_SIZE;
 
+	mutex_lock(&aspeed->lock);
+
 	switch (size) {
 	case 1:
 		ret = opb_writeb(aspeed, fsi_base + addr, *(u8 *)val);
@@ -298,14 +304,14 @@ static int aspeed_master_write(struct fsi_master *master, int link,
 		ret = opb_writel(aspeed, fsi_base + addr, *(__be32 *)val);
 		break;
 	default:
-		return -EINVAL;
+		ret = -EINVAL;
+		goto done;
 	}
 
 	ret = check_errors(aspeed, ret);
-	if (ret)
+done:
+	mutex_unlock(&aspeed->lock);
 	return ret;
-
-	return 0;
 }
 
 static int aspeed_master_link_enable(struct fsi_master *master, int link,
@@ -320,17 +326,21 @@ static int aspeed_master_link_enable(struct fsi_master *master, int link,
 
 	reg = cpu_to_be32(0x80000000 >> bit);
 
-	if (!enable)
-		return opb_writel(aspeed, ctrl_base + FSI_MCENP0 + (4 * idx),
-				  reg);
+	mutex_lock(&aspeed->lock);
+
+	if (!enable) {
+		ret = opb_writel(aspeed, ctrl_base + FSI_MCENP0 + (4 * idx), reg);
+		goto done;
+	}
 
 	ret = opb_writel(aspeed, ctrl_base + FSI_MSENP0 + (4 * idx), reg);
 	if (ret)
-		return ret;
+		goto done;
 
 	mdelay(FSI_LINK_ENABLE_SETUP_TIME);
-
-	return 0;
+done:
+	mutex_unlock(&aspeed->lock);
+	return ret;
 }
 
 static int aspeed_master_term(struct fsi_master *master, int link, uint8_t id)
@@ -431,9 +441,11 @@ static ssize_t cfam_reset_store(struct device *dev, struct device_attribute *att
 {
 	struct fsi_master_aspeed *aspeed = dev_get_drvdata(dev);
 
+	mutex_lock(&aspeed->lock);
 	gpiod_set_value(aspeed->cfam_reset_gpio, 1);
 	usleep_range(900, 1000);
 	gpiod_set_value(aspeed->cfam_reset_gpio, 0);
+	mutex_unlock(&aspeed->lock);
 
 	return count;
 }
@@ -597,6 +609,7 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(&pdev->dev, aspeed);
 
+	mutex_init(&aspeed->lock);
 	aspeed_master_init(aspeed);
 
 	rc = fsi_master_register(&aspeed->master);