Hi, On Mon, Nov 7, 2016 at 5:00 AM, William Wu <wulf@xxxxxxxxxxxxxx> wrote: > We found that the system crashed due to 480MHz output clock of > USB2 PHY was unstable after clock had been enabled by gpu module. > > Theoretically, 1 millisecond is a critical value for 480MHz > output clock stable time, so we try to change the delay time > to 1.2 millisecond to avoid this issue. > > Signed-off-by: William Wu <wulf@xxxxxxxxxxxxxx> > --- > drivers/phy/phy-rockchip-inno-usb2.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/phy/phy-rockchip-inno-usb2.c b/drivers/phy/phy-rockchip-inno-usb2.c > index ecfd7d1..8f2d2b6 100644 > --- a/drivers/phy/phy-rockchip-inno-usb2.c > +++ b/drivers/phy/phy-rockchip-inno-usb2.c > @@ -267,7 +267,7 @@ static int rockchip_usb2phy_clk480m_enable(struct clk_hw *hw) > return ret; > > /* waitting for the clk become stable */ > - mdelay(1); > + udelay(1200); Several people who have seen this patch have expressed concern that a 1.2 ms delay is pretty long for something that's supposed to be "atomic" like a clk_enable(). Consider that someone might call clk_enable() while interrupts are disabled and that a 1.2 ms interrupt latency is not so great. It seems like this clock should be moved to be enabled in "prepare" and the "enable" should be a no-op. This is a functionality change, but I don't think there are any real users for this clock at the moment so it should be fine. (of course, the 1 ms latency that existed before this patch was still pretty bad, but ...) -Doug -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
