ARM: tegra: fix USB ULPI PHY reset signal inversion confusion

[karo-tx-uboot.git] / drivers / usb / host / ehci-tegra.c

diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c
index eb54df471d90202fc6a3851d645332d360b5b630..e3620da15fb13974a089834861d4d47d202b2aca 100644 (file)
--- a/drivers/usb/host/ehci-tegra.c
+++ b/drivers/usb/host/ehci-tegra.c
@@ -600,9 +600,18 @@ static int init_ulpi_usb_controller(struct fdt_usb *config,
 
        /* reset ULPI phy */
        if (dm_gpio_is_valid(&config->phy_reset_gpio)) {
-               dm_gpio_set_value(&config->phy_reset_gpio, 0);
-               mdelay(5);
+               /*
+                * This GPIO is typically active-low, and marked as such in
+                * device tree. dm_gpio_set_value() takes this into account
+                * and inverts the value we pass here if required. In other
+                * words, this first call logically asserts the reset signal,
+                * which typically results in driving the physical GPIO low,
+                * and the second call logically de-asserts the reset signal,
+                * which typically results in driver the GPIO high.
+                */
                dm_gpio_set_value(&config->phy_reset_gpio, 1);
+               mdelay(5);
+               dm_gpio_set_value(&config->phy_reset_gpio, 0);
        }
 
        /* Reset the usb controller */