Hello Bin,
Quoting Bin Liu <b-liu@xxxxxx>:
On Thu, Feb 09, 2017 at 02:37:34AM -0600, Gustavo A. R. Silva wrote:
Hello everybody,
I ran into the following piece of code at
drivers/usb/musb/musb_core.c:1854 (linux-next)
1854/*
1855 * Check the musb devctl session bit to determine if we want to
1856 * allow PM runtime for the device. In general, we want to keep things
1857 * active when the session bit is set except after host disconnect.
1858 *
1859 * Only called from musb_irq_work. If this ever needs to get called
1860 * elsewhere, proper locking must be implemented for musb->session.
1861 */
1862static void musb_pm_runtime_check_session(struct musb *musb)
1863{
1864 u8 devctl, s;
1865 int error;
1866
1867 devctl = musb_readb(musb->mregs, MUSB_DEVCTL);
1868
1869 /* Handle session status quirks first */
1870 s = MUSB_DEVCTL_FSDEV | MUSB_DEVCTL_LSDEV |
1871 MUSB_DEVCTL_HR;
1872 switch (devctl & ~s) {
1873 case MUSB_QUIRK_B_INVALID_VBUS_91:
1874 if (musb->quirk_retries--) {
1875 musb_dbg(musb,
1876 "Poll devctl on invalid vbus,
assume no session");
1877 schedule_delayed_work(&musb->irq_work,
1878 msecs_to_jiffies(1000));
1879
1880 return;
1881 }
1882 case MUSB_QUIRK_A_DISCONNECT_19:
1883 if (musb->quirk_retries--) {
1884 musb_dbg(musb,
1885 "Poll devctl on possible host
mode disconnect");
1886 schedule_delayed_work(&musb->irq_work,
1887 msecs_to_jiffies(1000));
1888
1889 return;
1890 }
1891 if (!musb->session)
1892 break;
1893 musb_dbg(musb, "Allow PM on possible host mode
disconnect");
1894 pm_runtime_mark_last_busy(musb->controller);
1895 pm_runtime_put_autosuspend(musb->controller);
1896 musb->session = false;
1897 return;
1898 default:
1899 break;
1900 }
1901
1902 /* No need to do anything if session has not changed */
1903 s = devctl & MUSB_DEVCTL_SESSION;
1904 if (s == musb->session)
1905 return;
1906
1907 /* Block PM or allow PM? */
1908 if (s) {
1909 musb_dbg(musb, "Block PM on active session:
%02x", devctl);
1910 error = pm_runtime_get_sync(musb->controller);
1911 if (error < 0)
1912 dev_err(musb->controller, "Could not
enable: %i\n",
1913 error);
1914 musb->quirk_retries = 3;
1915 } else {
1916 musb_dbg(musb, "Allow PM with no session:
%02x", devctl);
1917 pm_runtime_mark_last_busy(musb->controller);
1918 pm_runtime_put_autosuspend(musb->controller);
1919 }
1920
1921 musb->session = s;
1922}
The thing is that the case for MUSB_QUIRK_B_INVALID_VBUS_91 is not
terminated by a break statement, and it falls through to the next
case MUSB_QUIRK_A_DISCONNECT_19, in case "if
(musb->quirk_retries--)" turns to be false.
My question here is if this code is intentional?
Yes, it is. For both MUSB_QUIRK_B_INVALID_VBUS_91 and
MUSB_QUIRK_A_DISCONNECT_19 cases, we first do retries, then if
musb->session is set, we allow PM.
Thanks for clarifying :)
--
Gustavo A. R. Silva
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