linux-kernel - [PATCH] clk: Re-evaluate clock rate on min/max update

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Date:   Tue, 21 Mar 2017 15:43:26 +0200
From:   Peter De Schrijver <pdeschrijver@...dia.com>
To:     Peter De Schrijver <pdeschrijver@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        <linux-clk@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] clk: Re-evaluate clock rate on min/max update

Whenever a user change its min or max rate limit of a clock, we need to
re-evaluate the current clock rate and possibly change it if the new limits
require so. To do this clk_set_rate_range() already calls
clk_core_set_rate_nolock, however this won't have the intended effect
because the core clock rate hasn't changed. To fix this, move the test to
avoid setting the same core clock rate again, to clk_set_rate() so
clk_core_set_rate_nolock() can change the clock rate when min or max have
been updated, even when the core clock rate has not changed.

Signed-off-by: Peter De Schrijver <pdeschrijver@...dia.com>
---
 drivers/clk/clk.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 2fa2fb8..0b815d1 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1569,10 +1569,6 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
 	if (!core)
 		return 0;
 
-	/* bail early if nothing to do */
-	if (rate == clk_core_get_rate_nolock(core))
-		return 0;
-
 	if ((core->flags & CLK_SET_RATE_GATE) && core->prepare_count)
 		return -EBUSY;
 
@@ -1621,16 +1617,21 @@ static int clk_core_set_rate_nolock(struct clk_core *core,
  */
 int clk_set_rate(struct clk *clk, unsigned long rate)
 {
-	int ret;
+	int ret = 0;
 
 	if (!clk)
-		return 0;
+		return ret;
 
 	/* prevent racing with updates to the clock topology */
 	clk_prepare_lock();
 
+	/* bail early if nothing to do */
+	if (rate == clk_core_get_rate_nolock(clk->core))
+		goto out;
+
 	ret = clk_core_set_rate_nolock(clk->core, rate);
 
+out:
 	clk_prepare_unlock();
 
 	return ret;
-- 
1.9.1