[PATCH 6/7] can: m_can: Add ECC functionality for message RAM

[Vivek Yadav <vivek.2311@samsung.com>]

Whenever MCAN Buffers and FIFOs are stored on message ram, there are
inherent risks of corruption known as single-bit errors.

Enable error correction code (ECC) data intigrity check for Message RAM
to create valid ECC checksums.

ECC uses a respective number of bits, which are added to each word as a
parity and that will raise the error signal on the corruption in the
Interrupt Register(IR).

Message RAM bit error controlled by input signal m_can_aeim_berr[0],
generated by an optional external parity / ECC logic attached to the
Message RAM.

This indicates either Bit Error detected and Corrected(BEC) or No bit
error detected when reading from Message RAM.

Signed-off-by: Vivek Yadav <vivek.2311@samsung.com>
---
 drivers/net/can/m_can/m_can.c | 73 +++++++++++++++++++++++++++++++++++
 drivers/net/can/m_can/m_can.h | 24 ++++++++++++
 2 files changed, 97 insertions(+)

diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
index dcb582563d5e..578146707d5b 100644
--- a/drivers/net/can/m_can/m_can.c
+++ b/drivers/net/can/m_can/m_can.c
@@ -1535,9 +1535,62 @@ static void m_can_stop(struct net_device *dev)
 	cdev->can.state = CAN_STATE_STOPPED;
 }
 
+int m_can_config_mram_ecc_check(struct m_can_classdev *cdev, int enable,
+				struct device_node *np)
+{
+	int val = 0;
+	int offset = 0, ret = 0;
+	int delay_count = MRAM_INIT_TIMEOUT;
+	struct m_can_mraminit *mraminit = &cdev->mraminit_sys;
+
+	mraminit->syscon = syscon_regmap_lookup_by_phandle(np,
+							   "mram-ecc-cfg");
+	if (IS_ERR(mraminit->syscon)) {
+		/* can fail with -EPROBE_DEFER */
+		ret = PTR_ERR(mraminit->syscon);
+		return ret;
+	}
+
+	if (of_property_read_u32_index(np, "mram-ecc-cfg", 1,
+				       &mraminit->reg)) {
+		dev_err(cdev->dev, "couldn't get the mraminit reg. offset!\n");
+		return -ENODEV;
+	}
+
+	val = ((MRAM_ECC_ENABLE_MASK | MRAM_CFG_VALID_MASK |
+		MRAM_INIT_ENABLE_MASK) << offset);
+	regmap_clear_bits(mraminit->syscon, mraminit->reg, val);
+
+	if (enable) {
+		val = (MRAM_ECC_ENABLE_MASK | MRAM_INIT_ENABLE_MASK) << offset;
+		regmap_set_bits(mraminit->syscon, mraminit->reg, val);
+	}
+
+	/* after enable or disable valid flag need to be set*/
+	val = (MRAM_CFG_VALID_MASK << offset);
+	regmap_set_bits(mraminit->syscon, mraminit->reg, val);
+
+	if (enable) {
+		do {
+			regmap_read(mraminit->syscon, mraminit->reg, &val);
+
+			if (val & (MRAM_INIT_DONE_MASK << offset))
+				return 0;
+
+			udelay(1);
+		} while (delay_count--);
+
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
 static int m_can_close(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
+	struct device_node *np;
+	int err = 0;
 
 	netif_stop_queue(dev);
 
@@ -1557,6 +1610,15 @@ static int m_can_close(struct net_device *dev)
 	if (cdev->is_peripheral)
 		can_rx_offload_disable(&cdev->offload);
 
+	np = cdev->dev->of_node;
+
+	if (np && of_property_read_bool(np, "mram-ecc-cfg")) {
+		err = m_can_config_mram_ecc_check(cdev, ECC_DISABLE, np);
+		if (err < 0)
+			netdev_err(dev,
+				   "Message RAM ECC disable config failed\n");
+	}
+
 	close_candev(dev);
 
 	phy_power_off(cdev->transceiver);
@@ -1754,6 +1816,7 @@ static int m_can_open(struct net_device *dev)
 {
 	struct m_can_classdev *cdev = netdev_priv(dev);
 	int err;
+	struct device_node *np;
 
 	err = phy_power_on(cdev->transceiver);
 	if (err)
@@ -1798,6 +1861,16 @@ static int m_can_open(struct net_device *dev)
 		goto exit_irq_fail;
 	}
 
+	np = cdev->dev->of_node;
+
+	if (np && of_property_read_bool(np, "mram-ecc-cfg")) {
+		err = m_can_config_mram_ecc_check(cdev, ECC_ENABLE, np);
+		if (err < 0) {
+			netdev_err(dev,
+				   "Message RAM ECC enable config failed\n");
+		}
+	}
+
 	/* start the m_can controller */
 	m_can_start(dev);
 
diff --git a/drivers/net/can/m_can/m_can.h b/drivers/net/can/m_can/m_can.h
index 4c0267f9f297..3cbfdc64a7db 100644
--- a/drivers/net/can/m_can/m_can.h
+++ b/drivers/net/can/m_can/m_can.h
@@ -28,6 +28,8 @@
 #include <linux/can/dev.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/phy/phy.h>
+#include <linux/mfd/syscon.h>
+#include <linux/regmap.h>
 
 /* m_can lec values */
 enum m_can_lec_type {
@@ -52,12 +54,33 @@ enum m_can_mram_cfg {
 	MRAM_CFG_NUM,
 };
 
+enum m_can_ecc_cfg {
+	ECC_DISABLE = 0,
+	ECC_ENABLE,
+};
+
 /* address offset and element number for each FIFO/Buffer in the Message RAM */
 struct mram_cfg {
 	u16 off;
 	u8  num;
 };
 
+/* MRAM_INIT_BITS */
+#define MRAM_CFG_VALID_SHIFT   5
+#define MRAM_CFG_VALID_MASK    BIT(MRAM_CFG_VALID_SHIFT)
+#define MRAM_ECC_ENABLE_SHIFT  3
+#define MRAM_ECC_ENABLE_MASK   BIT(MRAM_ECC_ENABLE_SHIFT)
+#define MRAM_INIT_ENABLE_SHIFT 1
+#define MRAM_INIT_ENABLE_MASK  BIT(MRAM_INIT_ENABLE_SHIFT)
+#define MRAM_INIT_DONE_SHIFT   0
+#define MRAM_INIT_DONE_MASK    BIT(MRAM_INIT_DONE_SHIFT)
+#define MRAM_INIT_TIMEOUT      50
+
+struct m_can_mraminit {
+	struct regmap *syscon;  /* for mraminit ctrl. reg. access */
+	unsigned int reg;       /* register index within syscon */
+};
+
 struct m_can_classdev;
 struct m_can_ops {
 	/* Device specific call backs */
@@ -92,6 +115,7 @@ struct m_can_classdev {
 	int pm_clock_support;
 	int is_peripheral;
 
+	struct m_can_mraminit mraminit_sys;     /* mraminit via syscon regmap */
 	struct mram_cfg mcfg[MRAM_CFG_NUM];
 };
 
-- 
2.17.1