can: sja1000: of: add compatibility with Technologic Systems version

Technologic Systems provides an IP compatible with the SJA1000,
instantiated in an FPGA. Because of some bus widths issue, access to
registers is made through a "window" that works like this:

    base + 0x0: address to read/write
    base + 0x2: 8-bit register value

This commit adds a new compatible device, "technologic,sja1000", with
read and write functions using the window mechanism.
Signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/sja1000/sja1000_platform.c

@@ -46,6 +46,10 @@ struct sja1000_of_data {
 	int     (*init)(struct sja1000_priv *priv, struct device_node *of);
 };
 
+struct technologic_priv {
+	spinlock_t      io_lock;
+};
+
 static u8 sp_read_reg8(const struct sja1000_priv *priv, int reg)
 {
 	return ioread8(priv->reg_base + reg);
@@ -76,6 +80,43 @@ static void sp_write_reg32(const struct sja1000_priv *priv, int reg, u8 val)
 	iowrite8(val, priv->reg_base + reg * 4);
 }
 
+static u8 sp_technologic_read_reg16(const struct sja1000_priv *priv, int reg)
+{
+	struct technologic_priv *tp = priv->priv;
+	unsigned long flags;
+	u8 val;
+
+	spin_lock_irqsave(&tp->io_lock, flags);
+	iowrite16(reg, priv->reg_base + 0);
+	val = ioread16(priv->reg_base + 2);
+	spin_unlock_irqrestore(&tp->io_lock, flags);
+
+	return val;
+}
+
+static void sp_technologic_write_reg16(const struct sja1000_priv *priv,
+				       int reg, u8 val)
+{
+	struct technologic_priv *tp = priv->priv;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tp->io_lock, flags);
+	iowrite16(reg, priv->reg_base + 0);
+	iowrite16(val, priv->reg_base + 2);
+	spin_unlock_irqrestore(&tp->io_lock, flags);
+}
+
+static int sp_technologic_init(struct sja1000_priv *priv, struct device_node *of)
+{
+	struct technologic_priv *tp = priv->priv;
+
+	priv->read_reg = sp_technologic_read_reg16;
+	priv->write_reg = sp_technologic_write_reg16;
+	spin_lock_init(&tp->io_lock);
+
+	return 0;
+}
+
 static void sp_populate(struct sja1000_priv *priv,
 			struct sja1000_platform_data *pdata,
 			unsigned long resource_mem_flags)
@@ -160,8 +201,14 @@ static void sp_populate_of(struct sja1000_priv *priv, struct device_node *of)
 		priv->cdr |= CDR_CBP; /* default */
 }
 
+static struct sja1000_of_data technologic_data = {
+	.priv_sz = sizeof(struct technologic_priv),
+	.init = sp_technologic_init,
+};
+
 static const struct of_device_id sp_of_table[] = {
 	{ .compatible = "nxp,sja1000", .data = NULL, },
+	{ .compatible = "technologic,sja1000", .data = &technologic_data, },
 	{ /* sentinel */ },
 };
 MODULE_DEVICE_TABLE(of, sp_of_table);