mtd: spi-nor: cadence-quadspi: add a delay in write sequence

As per 66AK2G02 TRM[1] SPRUHY8F section 11.15.5.3 Indirect Access
Controller programming sequence, a delay equal to couple of QSPI master
clock(~5ns) is required after setting CQSPI_REG_INDIRECTWR_START bit and
writing data to the flash. Introduce a quirk flag CQSPI_NEEDS_WR_DELAY
to handle this and set this flag for TI 66AK2G SoC.

[1]http://www.ti.com/lit/ug/spruhy8f/spruhy8f.pdf

Signed-off-by: Vignesh R <vigneshr@ti.com>
Acked-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>

drivers/mtd/spi-nor/cadence-quadspi.c

@@ -38,6 +38,9 @@
 #define CQSPI_NAME			"cadence-qspi"
 #define CQSPI_MAX_CHIPSELECT		16
 
+/* Quirks */
+#define CQSPI_NEEDS_WR_DELAY		BIT(0)
+
 struct cqspi_st;
 
 struct cqspi_flash_pdata {
@@ -76,6 +79,7 @@ struct cqspi_st {
 	u32			fifo_depth;
 	u32			fifo_width;
 	u32			trigger_address;
+	u32			wr_delay;
 	struct cqspi_flash_pdata f_pdata[CQSPI_MAX_CHIPSELECT];
 };
 
@@ -608,6 +612,15 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor,
 	reinit_completion(&cqspi->transfer_complete);
 	writel(CQSPI_REG_INDIRECTWR_START_MASK,
 	       reg_base + CQSPI_REG_INDIRECTWR);
+	/*
+	 * As per 66AK2G02 TRM SPRUHY8F section 11.15.5.3 Indirect Access
+	 * Controller programming sequence, couple of cycles of
+	 * QSPI_REF_CLK delay is required for the above bit to
+	 * be internally synchronized by the QSPI module. Provide 5
+	 * cycles of delay.
+	 */
+	if (cqspi->wr_delay)
+		ndelay(cqspi->wr_delay);
 
 	while (remaining > 0) {
 		write_bytes = remaining > page_size ? page_size : remaining;
@@ -1156,6 +1169,7 @@ static int cqspi_probe(struct platform_device *pdev)
 	struct cqspi_st *cqspi;
 	struct resource *res;
 	struct resource *res_ahb;
+	unsigned long data;
 	int ret;
 	int irq;
 
@@ -1213,6 +1227,10 @@ static int cqspi_probe(struct platform_device *pdev)
 	}
 
 	cqspi->master_ref_clk_hz = clk_get_rate(cqspi->clk);
+	data  = (unsigned long)of_device_get_match_data(dev);
+	if (data & CQSPI_NEEDS_WR_DELAY)
+		cqspi->wr_delay = 5 * DIV_ROUND_UP(NSEC_PER_SEC,
+						   cqspi->master_ref_clk_hz);
 
 	ret = devm_request_irq(dev, irq, cqspi_irq_handler, 0,
 			       pdev->name, cqspi);
@@ -1284,7 +1302,14 @@ static const struct dev_pm_ops cqspi__dev_pm_ops = {
 #endif
 
 static const struct of_device_id cqspi_dt_ids[] = {
-	{.compatible = "cdns,qspi-nor",},
+	{
+		.compatible = "cdns,qspi-nor",
+		.data = (void *)0,
+	},
+	{
+		.compatible = "ti,k2g-qspi",
+		.data = (void *)CQSPI_NEEDS_WR_DELAY,
+	},
 	{ /* end of table */ }
 };