On Wed, Oct 19, 2016 at 08:18:22AM +0800, Lu Baolu wrote: > +++ b/drivers/usb/early/xhci-dbc.c
> +static int xdbc_bulk_write(const char *bytes, int size) > +{ > + unsigned long flags; > + int ret, timeout = 0; > + > + spin_lock_irqsave(&xdbc.lock, flags); Yikes!! So how is this supposed to work from NMI context and the like? (also, at the very least, that should be a raw_spinlock_t) What do you need the spinlock for? Afaict this is a 'simple' polling event handling loop on MMIO, right? All we really need to guarantee is that there's only a single CPU trying to do that at any one time. Wouldn't something like: https://marc.info/?l=linux-kernel&m=147681099108509&w=2 already take care of that? Then you can drop the lock and things will work 'nested'. > + > + xdbc_handle_events(); > + > + /* Check completion of the previous request. */ > + while (xdbc.flags & XDBC_FLAGS_OUT_PROCESS) { > + if (timeout > 1000000) > + break; > + > + spin_unlock_irqrestore(&xdbc.lock, flags); > + xdbc_delay(100); > + spin_lock_irqsave(&xdbc.lock, flags); > + timeout += 100; > + > + xdbc_handle_events(); > + } > + > + if (xdbc.flags & XDBC_FLAGS_OUT_PROCESS) { > + spin_unlock_irqrestore(&xdbc.lock, flags); > + > + /* > + * Oops, hardware wasn't able to complete the > + * previous transfer. > + */ > + xdbc_trace("oops: previous transfer not completed yet\n"); > + > + return -ETIMEDOUT; > + } > + > + ret = xdbc_bulk_transfer((void *)bytes, size, false); > + > + spin_unlock_irqrestore(&xdbc.lock, flags); > + > + return ret; > +} > + > +static void early_xdbc_write(struct console *con, const char *str, u32 n) > +{ > + int chunk, ret; > + static char buf[XDBC_MAX_PACKET]; > + int use_cr = 0; > + > + if (!xdbc.xdbc_reg) > + return; > + memset(buf, 0, XDBC_MAX_PACKET); > + while (n > 0) { > + for (chunk = 0; chunk < XDBC_MAX_PACKET && n > 0; > + str++, chunk++, n--) { > + if (!use_cr && *str == '\n') { > + use_cr = 1; > + buf[chunk] = '\r'; > + str--; > + n++; > + continue; > + } > + if (use_cr) > + use_cr = 0; > + buf[chunk] = *str; > + } > + if (chunk > 0) { > + ret = xdbc_bulk_write(buf, chunk); > + if (ret < 0) > + break; > + } > + } > +} > + > +static struct console early_xdbc_console = { > + .name = "earlyxdbc", > + .write = early_xdbc_write, > + .flags = CON_PRINTBUFFER, > + .index = -1, > +}; > + > +void __init early_xdbc_register_console(void) > +{ > + if (early_console) > + return; > + > + early_console = &early_xdbc_console; > + if (early_console_keep) > + early_console->flags &= ~CON_BOOT; > + else > + early_console->flags |= CON_BOOT; > + register_console(early_console); > +} > + > +static void xdbc_scrub_function(struct work_struct *work) > +{ > + unsigned long flags; > + > + spin_lock_irqsave(&xdbc.lock, flags); > + > + /* > + * DbC is running, check the event ring and > + * handle the events. > + */ > + if (readl(&xdbc.xdbc_reg->control) & CTRL_DRC) > + xdbc_handle_events(); > + > + /* > + * External reset happened. Need to restart the > + * debugging hardware. > + */ > + if (unlikely(!(readl(&xdbc.xdbc_reg->control) & CTRL_DCE))) > + xdbc_handle_external_reset(); > + > + spin_unlock_irqrestore(&xdbc.lock, flags); > + > + queue_delayed_work(xdbc_wq, &xdbc.scrub, usecs_to_jiffies(100)); > +} Excuse my total lack of USB knowledge, but WTH does this do and what do we need it for? -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html