[PATCH] clk: do not trust cached rates for disabled clocks

[<rs@ti.com>]

From: Randolph Sapp <rs@ti.com>

Recalculate the clock rate for unprepared clocks. This cached value can
vary depending on the clocking architecture. On platforms with clocks
that have shared management it's possible that:

 - Previously disabled clocks have been enabled by other entities
 - Rates calculated during clock tree initialization could have changed

Signed-off-by: Randolph Sapp <rs@ti.com>
---

I'm hoping this will start a bit of a discussion. I'm still curious why people
would want to read the rate of an unprepared clock, but there were so many
logged operations on my test platforms that I assumed it must have some purpose.

Either way, I don't believe cached values should ever be trusted in this
scenario.

 drivers/clk/clk.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 85d2f2481acf..9c8b9036b6f6 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1971,8 +1971,16 @@ static void __clk_recalc_rates(struct clk_core *core, bool update_req,
 
 static unsigned long clk_core_get_rate_recalc(struct clk_core *core)
 {
-	if (core && (core->flags & CLK_GET_RATE_NOCACHE))
-		__clk_recalc_rates(core, false, 0);
+	if (core) {
+		bool prepared = clk_core_is_prepared(core);
+
+		if (core->flags & CLK_GET_RATE_NOCACHE || !prepared) {
+			if (!prepared)
+				pr_debug("%s: rate requested for unprepared clock %s\n",
+					 __func__, core->name);
+			__clk_recalc_rates(core, false, 0);
+		}
+	}
 
 	return clk_core_get_rate_nolock(core);
 }
-- 
2.51.0