usb: dwc3: xilinx: Add gpio-reset support

This patch adds a USB GPIO based reset for dwc3-xilinx driver. The PHY
needs to be reset after the completion of phy initialization. As part
of the reset, check for gpio-reset binding before toggling the pin.
This feature is advantageous when the user toggle GPIO to trigger the
ULPI-PHY reset.

Delay of milliseconds is added in between low and high to meet the setup
and hold time requirement of the reset. The reset-gpio error handling is
added for error notification.

Some GPIO controllers must be accessed using message-based buses, like
I2C or SPI, to address this problem, updates GPIO access with sleep API.

This reset is specific to the zynqMp.

Signed-off-by: Piyush Mehta <piyush.mehta@xilinx.com>
Link: https://lore.kernel.org/r/20220504075309.6244-3-piyush.mehta@xilinx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/dwc3/dwc3-xilinx.c b/drivers/usb/dwc3/dwc3-xilinx.c
index a6f3a9b..67b237c 100644 (file)
--- a/drivers/usb/dwc3/dwc3-xilinx.c
+++ b/drivers/usb/dwc3/dwc3-xilinx.c
@@ -13,6 +13,7 @@
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
+#include <linux/of_gpio.h>
 #include <linux/of_platform.h>
 #include <linux/pm_runtime.h>
 #include <linux/reset.h>
@@ -98,6 +99,7 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
 {
        struct device           *dev = priv_data->dev;
        struct reset_control    *crst, *hibrst, *apbrst;
+       struct gpio_desc        *reset_gpio;
        struct phy              *usb3_phy;
        int                     ret = 0;
        u32                     reg;
@@ -201,6 +203,21 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
        }
 
 skip_usb3_phy:
+       /* ulpi reset via gpio-modepin or gpio-framework driver */
+       reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+       if (IS_ERR(reset_gpio)) {
+               return dev_err_probe(dev, PTR_ERR(reset_gpio),
+                                    "Failed to request reset GPIO\n");
+       }
+
+       if (reset_gpio) {
+               /* Toggle ulpi to reset the phy. */
+               gpiod_set_value_cansleep(reset_gpio, 1);
+               usleep_range(5000, 10000);
+               gpiod_set_value_cansleep(reset_gpio, 0);
+               usleep_range(5000, 10000);
+       }
+
        /*
         * This routes the USB DMA traffic to go through FPD path instead
         * of reaching DDR directly. This traffic routing is needed to