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: 606397d67f41 ("fsi: Add ast2600 master driver")
Reviewed-by: Joel Stanley <[e-mail]>
Reviewed-by: Milton Miller <[e-mail]>
Signed-off-by: Eddie James <[e-mail]>
Signed-off-by: Joel Stanley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/fsi/fsi-master-aspeed.c

···
 #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>
···
 
 struct fsi_master_aspeed {
 	struct fsi_master	master;
+	struct mutex		lock;	/* protect HW access */
 	struct device		*dev;
 	void __iomem		*base;
 	struct clk		*clk;
···
 	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);
···
 		ret = opb_readl(aspeed, fsi_base + addr, val);
 		break;
 	default:
-		return -EINVAL;
+		ret = -EINVAL;
+		goto done;
 	}
 
 	ret = check_errors(aspeed, ret);
-	if (ret)
-		return ret;
-
-	return 0;
+done:
+	mutex_unlock(&aspeed->lock);
+	return ret;
 }
 
 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);
···
 		ret = opb_writel(aspeed, fsi_base + addr, *(__be32 *)val);
 		break;
 	default:
-		return -EINVAL;
+		ret = -EINVAL;
+		goto done;
 	}
 
 	ret = check_errors(aspeed, ret);
-	if (ret)
-		return ret;
-
-	return 0;
+done:
+	mutex_unlock(&aspeed->lock);
+	return ret;
 }
 
 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)
···
 {
 	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;
 }
···
 
 	dev_set_drvdata(&pdev->dev, aspeed);
 
+	mutex_init(&aspeed->lock);
 	aspeed_master_init(aspeed);
 
 	rc = fsi_master_register(&aspeed->master);