spi: bcm-qspi: Handle lack of MSPI_REV offset

Older MIPS chips have a QSPI/MSPI controller that does not have the
MSPI_REV offset, reading from that offset will cause a bus error. Match
their compatible string and do not perform a read from that register in
that case.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Link: https://lore.kernel.org/r/20200420190853.45614-4-kdasu.kdev@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm-qspi.c

@@ -91,6 +91,7 @@
 #define MSPI_MSPI_STATUS			0x020
 #define MSPI_CPTQP				0x024
 #define MSPI_SPCR3				0x028
+#define MSPI_REV				0x02c
 #define MSPI_TXRAM				0x040
 #define MSPI_RXRAM				0x0c0
 #define MSPI_CDRAM				0x140
@@ -217,6 +218,8 @@ struct bcm_qspi {
 	struct bcm_qspi_dev_id *dev_ids;
 	struct completion mspi_done;
 	struct completion bspi_done;
+	u8 mspi_maj_rev;
+	u8 mspi_min_rev;
 };
 
 static inline bool has_bspi(struct bcm_qspi *qspi)
@@ -1190,8 +1193,35 @@ static const struct spi_controller_mem_ops bcm_qspi_mem_ops = {
 	.exec_op = bcm_qspi_exec_mem_op,
 };
 
+struct bcm_qspi_data {
+	bool	has_mspi_rev;
+};
+
+static const struct bcm_qspi_data bcm_qspi_no_rev_data = {
+	.has_mspi_rev	= false,
+};
+
+static const struct bcm_qspi_data bcm_qspi_rev_data = {
+	.has_mspi_rev	= true,
+};
+
 static const struct of_device_id bcm_qspi_of_match[] = {
-	{ .compatible = "brcm,spi-bcm-qspi" },
+	{
+		.compatible = "brcm,spi-bcm7425-qspi",
+		.data = &bcm_qspi_no_rev_data,
+	},
+	{
+		.compatible = "brcm,spi-bcm7429-qspi",
+		.data = &bcm_qspi_no_rev_data,
+	},
+	{
+		.compatible = "brcm,spi-bcm7435-qspi",
+		.data = &bcm_qspi_no_rev_data,
+	},
+	{
+		.compatible = "brcm,spi-bcm-qspi",
+		.data = &bcm_qspi_rev_data,
+	},
 	{},
 };
 MODULE_DEVICE_TABLE(of, bcm_qspi_of_match);
@@ -1199,12 +1229,15 @@ MODULE_DEVICE_TABLE(of, bcm_qspi_of_match);
 int bcm_qspi_probe(struct platform_device *pdev,
 		   struct bcm_qspi_soc_intc *soc_intc)
 {
+	const struct of_device_id *of_id = NULL;
+	const struct bcm_qspi_data *data;
 	struct device *dev = &pdev->dev;
 	struct bcm_qspi *qspi;
 	struct spi_master *master;
 	struct resource *res;
 	int irq, ret = 0, num_ints = 0;
 	u32 val;
+	u32 rev = 0;
 	const char *name = NULL;
 	int num_irqs = ARRAY_SIZE(qspi_irq_tab);
 
@@ -1212,9 +1245,12 @@ int bcm_qspi_probe(struct platform_device *pdev,
 	if (!dev->of_node)
 		return -ENODEV;
 
-	if (!of_match_node(bcm_qspi_of_match, dev->of_node))
+	of_id = of_match_node(bcm_qspi_of_match, dev->of_node);
+	if (!of_id)
 		return -ENODEV;
 
+	data = of_id->data;
+
 	master = spi_alloc_master(dev, sizeof(struct bcm_qspi));
 	if (!master) {
 		dev_err(dev, "error allocating spi_master\n");
@@ -1351,6 +1387,16 @@ int bcm_qspi_probe(struct platform_device *pdev,
 	qspi->base_clk = clk_get_rate(qspi->clk);
 	qspi->max_speed_hz = qspi->base_clk / (QSPI_SPBR_MIN * 2);
 
+	if (data->has_mspi_rev) {
+		rev = bcm_qspi_read(qspi, MSPI, MSPI_REV);
+		/* some older revs do not have a MSPI_REV register */
+		if ((rev & 0xff) == 0xff)
+			rev = 0;
+	}
+
+	qspi->mspi_maj_rev = (rev >> 4) & 0xf;
+	qspi->mspi_min_rev = rev & 0xf;
+
 	bcm_qspi_hw_init(qspi);
 	init_completion(&qspi->mspi_done);
 	init_completion(&qspi->bspi_done);