| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 128/158] usb: phy: am335x-control: wait 1ms after power-up transitions | Date | Sun, 4 May 2014 11:40:37 -0400 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Daniel Mack <zonque@gmail.com>
commit a31a942a148e0083ce560ffeb54fb60e06ab7201 upstream.
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> Signed-off-by: Felipe Balbi <balbi@ti.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/usb/phy/phy-am335x-control.c | 9 +++++++++ 1 file changed, 9 insertions(+)
--- 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 @@ static void am335x_phy_power(struct phy_ } 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 = {
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