linux-kernel - [PATCH v2 5/5] clk: Get runtime PM before walking tree for clk

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Date: Mon, 25 Mar 2024 11:41:59 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>
Cc: linux-kernel@...r.kernel.org,
	linux-clk@...r.kernel.org,
	patches@...ts.linux.dev,
	linux-arm-msm@...r.kernel.org,
	Taniya Das <quic_tdas@...cinc.com>,
	Douglas Anderson <dianders@...omium.org>
Subject: [PATCH v2 5/5] clk: Get runtime PM before walking tree for clk_summary

Similar to the previous commit, we should make sure that all devices are
runtime resumed before printing the clk_summary through debugfs. Failure
to do so would result in a deadlock if the thread is resuming a device
to print clk state and that device is also runtime resuming in another
thread, e.g the screen is turning on and the display driver is starting
up. We remove the calls to clk_pm_runtime_{get,put}() in this path
because they're superfluous now that we know the devices are runtime
resumed. This also squashes a bug where the return value of
clk_pm_runtime_get() wasn't checked, leading to an RPM count underflow
on error paths.

Fixes: 1bb294a7981c ("clk: Enable/Disable runtime PM for clk_summary")
Cc: Taniya Das <quic_tdas@...cinc.com>
Cc: Douglas Anderson <dianders@...omium.org>
Signed-off-by: Stephen Boyd <sboyd@...nel.org>
---
 drivers/clk/clk.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index c69de47afaba..3539675ea846 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -3318,9 +3318,7 @@ static void clk_summary_show_subtree(struct seq_file *s, struct clk_core *c,
 {
 	struct clk_core *child;
 
-	clk_pm_runtime_get(c);
 	clk_summary_show_one(s, c, level);
-	clk_pm_runtime_put(c);
 
 	hlist_for_each_entry(child, &c->children, child_node)
 		clk_summary_show_subtree(s, child, level + 1);
@@ -3330,11 +3328,15 @@ static int clk_summary_show(struct seq_file *s, void *data)
 {
 	struct clk_core *c;
 	struct hlist_head **lists = s->private;
+	int ret;
 
 	seq_puts(s, "                                 enable  prepare  protect                                duty  hardware                            connection\n");
 	seq_puts(s, "   clock                          count    count    count        rate   accuracy phase  cycle    enable   consumer                         id\n");
 	seq_puts(s, "---------------------------------------------------------------------------------------------------------------------------------------------\n");
 
+	ret = clk_pm_runtime_get_all();
+	if (ret)
+		return ret;
 
 	clk_prepare_lock();
 
@@ -3343,6 +3345,7 @@ static int clk_summary_show(struct seq_file *s, void *data)
 			clk_summary_show_subtree(s, c, 0);
 
 	clk_prepare_unlock();
+	clk_pm_runtime_put_all();
 
 	return 0;
 }
@@ -3390,8 +3393,14 @@ static int clk_dump_show(struct seq_file *s, void *data)
 	struct clk_core *c;
 	bool first_node = true;
 	struct hlist_head **lists = s->private;
+	int ret;
+
+	ret = clk_pm_runtime_get_all();
+	if (ret)
+		return ret;
 
 	seq_putc(s, '{');
+
 	clk_prepare_lock();
 
 	for (; *lists; lists++) {
@@ -3404,6 +3413,7 @@ static int clk_dump_show(struct seq_file *s, void *data)
 	}
 
 	clk_prepare_unlock();
+	clk_pm_runtime_put_all();
 
 	seq_puts(s, "}\n");
 	return 0;
-- 
https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git/
https://git.kernel.org/pub/scm/linux/kernel/git/sboyd/spmi.git