[PATCH 4/4] spi: spi-nxp-fspi: add function to select sample clock source for flash reading

[haibo.chen@xxxxxxx]

From: Haibo Chen <haibo.chen@xxxxxxx>

fspi define four mode for sample clock source selection.

Here is the list of modes:
mode 0: Dummy Read strobe generated by FlexSPI Controller and loopback internally
mode 1: Dummy Read strobe generated by FlexSPI Controller and loopback from DQS pad
mode 2: Reserved
mode 3: Flash provided Read strobe and input from DQS pad

In default, fspi use mode 0 after reset.
For 8-8-8-DTR mode, need to use mode 3, otherwise 8-8-8-DTR read always
get incorrect data.

Signed-off-by: Haibo Chen <haibo.chen@xxxxxxx>
---
 drivers/spi/spi-nxp-fspi.c | 46 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/drivers/spi/spi-nxp-fspi.c b/drivers/spi/spi-nxp-fspi.c
index f7acad2cbe64..309685a6d493 100644
--- a/drivers/spi/spi-nxp-fspi.c
+++ b/drivers/spi/spi-nxp-fspi.c
@@ -377,6 +377,7 @@ struct nxp_fspi {
 	struct pm_qos_request pm_qos_req;
 	int selected;
 #define FSPI_INITILIZED		(1 << 0)
+#define FSPI_RXCLKSRC_3		(1 << 1)
 	int flags;
 };
 
@@ -877,6 +878,49 @@ static int nxp_fspi_do_op(struct nxp_fspi *f, const struct spi_mem_op *op)
 	return err;
 }
 
+/*
+ * Sample Clock source selection for Flash Reading
+ * Four modes defined by fspi:
+ * mode 0: Dummy Read strobe generated by FlexSPI Controller
+ *         and loopback internally
+ * mode 1: Dummy Read strobe generated by FlexSPI Controller
+ *         and loopback from DQS pad
+ * mode 2: Reserved
+ * mode 3: Flash provided Read strobe and input from DQS pad
+ *
+ * fspi default use mode 0 after reset
+ */
+static void nxp_fspi_select_rx_sample_clk_source(struct nxp_fspi *f)
+{
+	u32 reg;
+
+	/*
+	 * For 8-8-8-DTR mode, need to use mode 3 (Flash provided Read
+	 * strobe and input from DQS pad), otherwise read operaton may
+	 * meet issue.
+	 * This mode require flash device connect the DQS pad on board.
+	 * For other modes, still use mode 0, keep align with before.
+	 * spi_nor_suspend will disable 8-8-8-DTR mode, also need to
+	 * change the mode back to mode 0.
+	 */
+	if (!(f->flags & FSPI_RXCLKSRC_3) &&
+			op->cmd.dtr && op->addr.dtr &&
+			op->dummy.dtr && op->data.dtr) {
+		reg = fspi_readl(f, f->iobase + FSPI_MCR0);
+		reg |= FSPI_MCR0_RXCLKSRC(3);
+		fspi_writel(f, reg, f->iobase + FSPI_MCR0);
+		f->flags |= FSPI_RXCLKSRC_3;
+	} else if ((f->flags & FSPI_RXCLKSRC_3) &&
+			!op->cmd.dtr && !op->addr.dtr &&
+			!op->dummy.dtr && !op->data.dtr) {
+		reg = fspi_readl(f, f->iobase + FSPI_MCR0);
+		reg &= ~FSPI_MCR0_RXCLKSRC(3);	/* select mode 0 */
+		fspi_writel(f, reg, f->iobase + FSPI_MCR0);
+		f->flags &= ~FSPI_RXCLKSRC_3;
+	}
+
+}
+
 static int nxp_fspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 {
 	struct nxp_fspi *f = spi_controller_get_devdata(mem->spi->master);
@@ -897,6 +941,8 @@ static int nxp_fspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
 
 	nxp_fspi_select_mem(f, mem->spi);
 
+	nxp_fspi_select_rx_sample_clk_source(f);
+
 	nxp_fspi_prepare_lut(f, op);
 	/*
 	 * If we have large chunks of data, we read them through the AHB bus by
-- 
2.17.1