[PATCH net-next v2 2/9] net: ethernet: oa_tc6: implement mac-phy software reset

[Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>]

Reset complete bit is set when the MAC-PHY reset completes and ready for
configuration. When it is set, it will generate a non-maskable interrupt
to alert the SPI host. Additionally reset complete bit in the STS0
register has to be written by one upon reset complete to clear the
interrupt.

Signed-off-by: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
---
 drivers/net/ethernet/oa_tc6.c | 64 ++++++++++++++++++++++++++++++++---
 include/linux/oa_tc6.h        |  9 +++++
 2 files changed, 69 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index acedc327b05e..e4457569135f 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -6,6 +6,8 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
 #include <linux/oa_tc6.h>
 
 /* Opaque structure for MACPHY drivers */
@@ -169,10 +171,15 @@ static int oa_tc6_perform_ctrl(struct oa_tc6 *tc6, u32 addr, u32 val[], u8 len,
 	if (ret)
 		return ret;
 
-	/* Check echoed/received control reply for errors */
-	ret = oa_tc6_check_control(tc6, tx_buf, rx_buf, len, wnr, prote);
-	if (ret)
-		return ret;
+	/* In case of reset write, the echoed control command doesn't have any
+	 * valid data. So no need to check for errors.
+	 */
+	if (addr != RESET) {
+		/* Check echoed/received control reply for errors */
+		ret = oa_tc6_check_control(tc6, tx_buf, rx_buf, len, wnr, prote);
+		if (ret)
+			return ret;
+	}
 
 	if (!wnr) {
 		/* Copy read data from the rx data in case of ctrl read */
@@ -191,6 +198,49 @@ static int oa_tc6_perform_ctrl(struct oa_tc6 *tc6, u32 addr, u32 val[], u8 len,
 	return ret;
 }
 
+static int oa_tc6_sw_reset(struct oa_tc6 *tc6)
+{
+	u32 regval;
+	int ret;
+
+	/* Perform software reset with both protected and unprotected control
+	 * commands because the driver doesn't know the current status of the
+	 * MAC-PHY.
+	 */
+	regval = SWRESET;
+	ret = oa_tc6_perform_ctrl(tc6, RESET, &regval, 1, true, true);
+	if (ret)
+		return ret;
+
+	ret = oa_tc6_perform_ctrl(tc6, RESET, &regval, 1, true, false);
+	if (ret)
+		return ret;
+
+	/* The chip completes a reset in 3us, we might get here earlier than
+	 * that, as an added margin we'll conditionally sleep 5us.
+	 */
+	udelay(5);
+
+	ret = oa_tc6_perform_ctrl(tc6, STATUS0, &regval, 1, false, false);
+	if (ret)
+		return ret;
+
+	/* Check for reset complete interrupt status */
+	if (regval & RESETC) {
+		regval = RESETC;
+		/* SPI host should write RESETC bit with one to
+		 * clear the reset interrupt status.
+		 */
+		ret = oa_tc6_perform_ctrl(tc6, STATUS0, &regval, 1, true, false);
+		if (ret)
+			return ret;
+	} else {
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
 /**
  * oa_tc6_write_register - function for writing a MACPHY register.
  * @tc6: oa_tc6 struct.
@@ -279,6 +329,12 @@ struct oa_tc6 *oa_tc6_init(struct spi_device *spi, bool prote)
 	tc6->spi = spi;
 	tc6->prote = prote;
 
+	/* Perform MAC-PHY software reset */
+	if (oa_tc6_sw_reset(tc6)) {
+		dev_err(&spi->dev, "MAC-PHY software reset failed\n");
+		return NULL;
+	}
+
 	return tc6;
 }
 EXPORT_SYMBOL_GPL(oa_tc6_init);
diff --git a/include/linux/oa_tc6.h b/include/linux/oa_tc6.h
index 6284828bda42..8a838499da97 100644
--- a/include/linux/oa_tc6.h
+++ b/include/linux/oa_tc6.h
@@ -21,6 +21,15 @@
 #define TC6_FTR_SIZE		4	/* Ctrl command footer size ss per OA */
 #define TC6_CTRL_BUF_SIZE	1032	/* Max ctrl buffer size for 128 regs */
 
+/* Open Alliance TC6 Standard Control and Status Registers */
+/* Reset Control and Status Register */
+#define RESET			0x0003
+#define SWRESET			BIT(0)	/* Software Reset */
+
+/* Status Register #0 */
+#define STATUS0			0x0008
+#define RESETC			BIT(6)	/* Reset Complete */
+
 struct oa_tc6 *oa_tc6_init(struct spi_device *spi, bool prote);
 int oa_tc6_write_register(struct oa_tc6 *tc6, u32 addr, u32 val);
 int oa_tc6_read_register(struct oa_tc6 *tc6, u32 addr, u32 *val);
-- 
2.34.1