[PATCH 14/16] fpga: machxo2: add program initialization signalling via gpio

[Johannes Zink <j.zink@xxxxxxxxxxxxxx>]

Before initiating the programming sequence, this patch generates a low
pulse on FPGA's program_n pin which enables the FPGA's in circuit
programming interface.

Signed-off-by: Johannes Zink <j.zink@xxxxxxxxxxxxxx>
---
 drivers/fpga/machxo2-common.c | 15 +++++++++++++++
 drivers/fpga/machxo2-common.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/drivers/fpga/machxo2-common.c b/drivers/fpga/machxo2-common.c
index d93c304cceb9..ccf9a50fc590 100644
--- a/drivers/fpga/machxo2-common.c
+++ b/drivers/fpga/machxo2-common.c
@@ -167,6 +167,17 @@ static int machxo2_write_init(struct fpga_manager *mgr,
 		return -ENOTSUPP;
 	}
 
+	if (priv->fpga_program_n) {
+		/* set fpga in program mode. The timing is chosen very
+		 * conservatively, since the MachXO2 Family Datasheet
+		 * indicates a low pulse longer than 55ns will be accepted
+		 */
+		gpiod_set_value_cansleep(priv->fpga_program_n, 1);
+		usleep_range(1000, 1500);
+		gpiod_set_value_cansleep(priv->fpga_program_n, 0);
+		usleep_range(1000, 1500);
+	}
+
 	priv->get_status(priv, &status);
 	dump_status_reg(priv->dev, status);
 
@@ -331,6 +342,10 @@ int machxo2_common_init(struct machxo2_common_priv *priv, struct device *dev)
 
 	priv->erase_cmd = cpu_to_be32(erase_cmd);
 
+	priv->fpga_program_n = devm_gpiod_get_optional(dev,
+						       "lattice,program",
+						       GPIOD_OUT_LOW);
+
 	priv->dev = dev;
 
 	mgr = devm_fpga_mgr_register(dev, "Lattice MachXO2 SPI FPGA Manager",
diff --git a/drivers/fpga/machxo2-common.h b/drivers/fpga/machxo2-common.h
index 1b54154f91b1..0f9f53b48152 100644
--- a/drivers/fpga/machxo2-common.h
+++ b/drivers/fpga/machxo2-common.h
@@ -32,6 +32,7 @@ struct machxo2_common_priv {
 	int (*get_status)(struct machxo2_common_priv *priv, u32 *status);
 	struct device *dev;
 	__be32 erase_cmd;
+	struct gpio_desc *fpga_program_n;
 };
 
 int machxo2_common_init(struct machxo2_common_priv *priv, struct device *dev);
-- 
2.30.2