driver core: Don't require dynamic_debug for initcall_debug probe timing

commit e2f06aa upstream.

Don't require the use of dynamic debug (or modification of the kernel to
add a #define DEBUG to the top of this file) to get the printk message
about driver probe timing. This printk is only emitted when
initcall_debug is enabled on the kernel commandline, and it isn't
immediately obvious that you have to do something else to debug boot
timing issues related to driver probe. Add a comment too so it doesn't
get converted back to pr_debug().

Fixes: eb7fbc9 ("driver core: Add missing '\n' in log messages")
Cc: stable <stable@kernel.org>
Cc: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc: Brian Norris <briannorris@chromium.org>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/20230412225842.3196599-1-swboyd@chromium.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/dd.c

@@ -718,7 +718,12 @@ static int really_probe_debug(struct device *dev, struct device_driver *drv)
 	calltime = ktime_get();
 	ret = really_probe(dev, drv);
 	rettime = ktime_get();
-	pr_debug("probe of %s returned %d after %lld usecs\n",
+	/*
+	 * Don't change this to pr_debug() because that requires
+	 * CONFIG_DYNAMIC_DEBUG and we want a simple 'initcall_debug' on the
+	 * kernel commandline to print this all the time at the debug level.
+	 */
+	printk(KERN_DEBUG "probe of %s returned %d after %lld usecs\n",
 		 dev_name(dev), ret, ktime_us_delta(rettime, calltime));
 	return ret;
 }