can: grcan: grcan_probe(): fix broken system id check for errata workaround needs

The systemid property was checked for in the wrong place of the device
tree and compared to the wrong value.

Fixes: 6cec9b07 ("can: grcan: Add device driver for GRCAN and GRHCAN cores")
Link: https://lore.kernel.org/all/20220429084656.29788-3-andreas@gaisler.com
Cc: stable@vger.kernel.org
Signed-off-by: Andreas Larsson <andreas@gaisler.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/grcan.c

@@ -241,7 +241,7 @@ struct grcan_device_config {
 		.rxsize		= GRCAN_DEFAULT_BUFFER_SIZE,	\
 		}
 
-#define GRCAN_TXBUG_SAFE_GRLIB_VERSION	0x4100
+#define GRCAN_TXBUG_SAFE_GRLIB_VERSION	4100
 #define GRLIB_VERSION_MASK		0xffff
 
 /* GRCAN private data structure */
@@ -1643,6 +1643,7 @@ static int grcan_setup_netdev(struct platform_device *ofdev,
 static int grcan_probe(struct platform_device *ofdev)
 {
 	struct device_node *np = ofdev->dev.of_node;
+	struct device_node *sysid_parent;
 	u32 sysid, ambafreq;
 	int irq, err;
 	void __iomem *base;
@@ -1651,10 +1652,15 @@ static int grcan_probe(struct platform_device *ofdev)
 	/* Compare GRLIB version number with the first that does not
 	 * have the tx bug (see start_xmit)
 	 */
-	err = of_property_read_u32(np, "systemid", &sysid);
-	if (!err && ((sysid & GRLIB_VERSION_MASK)
-		     >= GRCAN_TXBUG_SAFE_GRLIB_VERSION))
+	sysid_parent = of_find_node_by_path("/ambapp0");
+	if (sysid_parent) {
+		of_node_get(sysid_parent);
+		err = of_property_read_u32(sysid_parent, "systemid", &sysid);
+		if (!err && ((sysid & GRLIB_VERSION_MASK) >=
+			     GRCAN_TXBUG_SAFE_GRLIB_VERSION))
 			txbug = false;
+		of_node_put(sysid_parent);
+	}
 
 	err = of_property_read_u32(np, "freq", &ambafreq);
 	if (err) {