Busy loops that poll on a register should call cpu_relax(). On some architectures, it can lower CPU power consumption or yield to a hyperthreaded twin processor. It also serves as a compiler barrier, see Documentation/process/volatile-considered-harmful.rst. In addition, if something goes wrong in the busy loop at least it can prevent things from getting worse. Signed-off-by: Zhongqiu Han <quic_zhonhan@xxxxxxxxxxx> --- drivers/usb/dwc3/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c index 734de2a8bd21..498f08dbbdb5 100644 --- a/drivers/usb/dwc3/core.c +++ b/drivers/usb/dwc3/core.c @@ -2050,6 +2050,8 @@ static int dwc3_get_num_ports(struct dwc3 *dwc) if (!offset) break; + cpu_relax(); + val = readl(base + offset); major_revision = XHCI_EXT_PORT_MAJOR(val); -- 2.25.1
