[PATCH net-next v2 2/2] net: ethernet: oa_tc6: add reset-gpios support

[Alessandro Zini <alessandro.zini@siemens.com>]

OPEN Alliance 10BASE-T1x MAC-PHY Serial Interface specification
(v1.1, Section 8.2) defines an external RESET pin as an optional reset
source for the MAC-PHY.

Add support for an optional reset GPIO in oa_tc6_init(). If specified in
the device tree, assert the hardware reset line for 10 us and allow 1 ms
settle time for crystal oscillator startup before performing the initial
TC6 control protection check and software reset.

Suggested-by: Parthiban Veerasooran <parthiban.veerasooran@microchip.com>
Signed-off-by: Alessandro Zini <alessandro.zini@siemens.com>
---
Changes in v2:
- Moved reset GPIO handling from lan865x.c to common oa_tc6.c as suggested
  by Parthiban Veerasooran.

 drivers/net/ethernet/oa_tc6.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/net/ethernet/oa_tc6.c b/drivers/net/ethernet/oa_tc6.c
index 6fcc5f561d560..a697e2cb99cd8 100644
--- a/drivers/net/ethernet/oa_tc6.c
+++ b/drivers/net/ethernet/oa_tc6.c
@@ -11,6 +11,8 @@
 #include <linux/mdio.h>
 #include <linux/phy.h>
 #include <linux/oa_tc6.h>
+#include <linux/gpio/consumer.h>
+#include <linux/delay.h>
 
 /* Control command header */
 #define OA_TC6_CTRL_HEADER_DATA_NOT_CTRL	BIT(31)
@@ -88,6 +90,7 @@ struct oa_tc6 {
 	bool disable_traffic;
 	bool prot_ctrl;
 	enum oa_tc6_quirk_flag quirk_flags;
+	struct gpio_desc *reset_gpio;
 };
 
 enum oa_tc6_header_type {
@@ -1503,6 +1506,24 @@ struct oa_tc6 *oa_tc6_init(struct spi_device *spi, struct net_device *netdev,
 	if (!tc6->spi_data_rx_buf)
 		return NULL;
 
+	tc6->reset_gpio = devm_gpiod_get_optional(&spi->dev, "reset",
+						  GPIOD_OUT_LOW);
+	if (IS_ERR(tc6->reset_gpio)) {
+		dev_err_probe(&spi->dev, PTR_ERR(tc6->reset_gpio),
+			      "Failed to get reset GPIO\n");
+		return NULL;
+	}
+
+	if (tc6->reset_gpio) {
+		/* Assert hardware reset for 10 us (datasheet specifies min 5 us)
+		 * and allow 1 ms settle time for crystal oscillator startup.
+		 */
+		gpiod_set_value_cansleep(tc6->reset_gpio, 1);
+		fsleep(10);
+		gpiod_set_value_cansleep(tc6->reset_gpio, 0);
+		fsleep(1000);
+	}
+
 	/* Check the PROTE bit status so that we can reset the device */
 	ret = oa_tc6_check_ctrl_protection(tc6);
 	if (ret) {
-- 
2.55.0