usb: phy: am335x-control: wait 1ms after power-up transitions
Tests have shown that when a power-up transition is followed by other
PHY operations too quickly, the USB port appears dead. Waiting 1ms fixes
this problem.
Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: stable@vger.kernel.org [3.14]
Signed-off-by: Felipe Balbi <balbi@ti.com>
diff --git a/drivers/usb/phy/phy-am335x-control.c b/drivers/usb/phy/phy-am335x-control.c
index d75196a..35b6083 100644
--- a/drivers/usb/phy/phy-am335x-control.c
+++ b/drivers/usb/phy/phy-am335x-control.c
@@ -3,6 +3,7 @@
#include <linux/err.h>
#include <linux/of.h>
#include <linux/io.h>
+#include <linux/delay.h>
#include "am35x-phy-control.h"
struct am335x_control_usb {
@@ -86,6 +87,14 @@
}
writel(val, usb_ctrl->phy_reg + reg);
+
+ /*
+ * Give the PHY ~1ms to complete the power up operation.
+ * Tests have shown unstable behaviour if other USB PHY related
+ * registers are written too shortly after such a transition.
+ */
+ if (on)
+ mdelay(1);
}
static const struct phy_control ctrl_am335x = {