linux-kernel - [PATCH] driver core: Don't require dynamic_debug for initcall

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Date:   Wed, 12 Apr 2023 15:58:42 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Brian Norris <briannorris@...omium.org>
Subject: [PATCH] driver core: Don't require dynamic_debug for initcall_debug probe timing

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: eb7fbc9fb118 ("driver core: Add missing '\n' in log messages")
Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Brian Norris <briannorris@...omium.org>
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
---
 drivers/base/dd.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 8def2ba08a82..1b16e0fb7658 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -708,7 +708,12 @@ 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;
 }

base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6
-- 
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