can: tcan4x5x: Check size of mram configuration

To reduce debugging effort in case the mram is misconfigured, add this
size check of the DT configuration. Currently if the mram configuration
doesn't fit into the available MRAM it just overwrites other areas of
the MRAM.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Link: https://lore.kernel.org/all/20230728141923.162477-4-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/m_can/m_can.c

@@ -1913,6 +1913,22 @@ static int register_m_can_dev(struct net_device *dev)
 	return register_candev(dev);
 }
 
+int m_can_check_mram_cfg(struct m_can_classdev *cdev, u32 mram_max_size)
+{
+	u32 total_size;
+
+	total_size = cdev->mcfg[MRAM_TXB].off - cdev->mcfg[MRAM_SIDF].off +
+			cdev->mcfg[MRAM_TXB].num * TXB_ELEMENT_SIZE;
+	if (total_size > mram_max_size) {
+		dev_err(cdev->dev, "Total size of mram config(%u) exceeds mram(%u)\n",
+			total_size, mram_max_size);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(m_can_check_mram_cfg);
+
 static void m_can_of_parse_mram(struct m_can_classdev *cdev,
 				const u32 *mram_config_vals)
 {

drivers/net/can/m_can/m_can.h

@@ -103,6 +103,7 @@ int m_can_class_register(struct m_can_classdev *cdev);
 void m_can_class_unregister(struct m_can_classdev *cdev);
 int m_can_class_get_clocks(struct m_can_classdev *cdev);
 int m_can_init_ram(struct m_can_classdev *priv);
+int m_can_check_mram_cfg(struct m_can_classdev *cdev, u32 mram_max_size);
 
 int m_can_class_suspend(struct device *dev);
 int m_can_class_resume(struct device *dev);

drivers/net/can/m_can/tcan4x5x-core.c

@@ -80,6 +80,7 @@
 	 TCAN4X5X_MCAN_IR_RF1F)
 
 #define TCAN4X5X_MRAM_START 0x8000
+#define TCAN4X5X_MRAM_SIZE 0x800
 #define TCAN4X5X_MCAN_OFFSET 0x1000
 
 #define TCAN4X5X_CLEAR_ALL_INT 0xffffffff
@@ -307,6 +308,10 @@ static int tcan4x5x_can_probe(struct spi_device *spi)
 	if (!mcan_class)
 		return -ENOMEM;
 
+	ret = m_can_check_mram_cfg(mcan_class, TCAN4X5X_MRAM_SIZE);
+	if (ret)
+		goto out_m_can_class_free_dev;
+
 	priv = cdev_to_priv(mcan_class);
 
 	priv->power = devm_regulator_get_optional(&spi->dev, "vsup");